Madgui

- add true 3D OpenGL based survey widget (WIP)
- fix exception in curvemanager tool when clicking snapshot button
- fix TypeError when importing a table without a text column
- show warning when entering invalid number format (instead of silently
ignoring the invalid input)
- show warnings when ignoring invalid knob strings

Improvements:

- add x/y/px/py values to *Twiss* tab in element info dialog
- replot backtracked twiss on every new monitor readout
- consider ``SBEND->K0`` when detecting knobs
- remove conversion mechanism for knobs, this is now the responsibility of the
model itself (by using appropriate expressions) or the online plugin
- use only user defined variables in deferred expressions as knobs, consider
fixed numbers as static
- show marks with monitor width/position when opening monitor dialog, can
select which ones to show
- add update/backtrack functionality to monitor widget
- show unit on the column title
- add simple data export for monitors
- make the monitorwidget child to the main window (so it will be closed like
everything else when the main window is closed)
- persist some settings across multiple madgui runs using *session* files:
main window size/position, model, folder, selected monitors
- enable grid in twiss plot (mainly for y=0)
- add ``onload`` config entry for application, and in model
- remove setuptools based entrypoint for online models, must be manually
loaded by the user using the ``onload`` handler instead
- draw element markers at the exit end of the element
- unify log window with MAD-X input commands, output, as well as logging
records, based on PlainTextEdit with extra selections in different colors,
much easier on the eyes and hands! Shows line numbers and times on the left.
- show exceptions in log window as well
- silence Pint redefinition warning
- log interleaved MAD-X input/output in chronological order!
- display line numbers for config edit dialog (multi grid)
- show only the actual MAD-X command parameters in the second info tab
- add ``kick`` attribute for SBEND in summary tab

Bug fixes:

- fix exception on py34: missing ``math.isclose``
- fix exception in floor plan
- fix error in matching due to discarding ``Expression``
- fix unit conversion for gantry angle
- fix multi grid with ``assign`` in config file
- use float edit boxes for target values
- fix input unit of multi-grid target values
- fix bug with disappearing monitor widget (GC related)

Internal changes:

- use function call syntax to get the values from Bool proxies
- remove some remaining py2 compatibility code
- support attribute access and *on_change* signals for config entries, make
``config.NumberFormat`` a simple config entry
- rename ``user_ns`` to ``context``
- cleanup some unused imports, undefined names etc (pyflakes)
- replace ``monospace`` function by a simpler one without ``size`` parameter
- remove uppercase restritcion when accessing element attributes
- adapt to changes in cpymad 1.0 API
- flip definition of ``gantry_angle`` (``SROTATION->ANGLE`` has changed in
MAD-X 5.04.00)

- Add Optic Variation Method for orbit flattening
- Add Sphinx V4.2.4 as default for documentation

- simplify the activate logic of the curvemanager tool (was a toggle item with
complex behaviour, is now simply a button that will create the widget)
- add "Ok" button for curvemanager widget
- fix beam diagnostic dialog staying open with blank tab when pressing Ok
- remove explicit dependency on minrpc version from setup.py (possibly fixes
problem where cpymad's requirement on the minrpc version is then ignored)
- improve knob selection/input in match dialog
- change how "assign" expressions must be defined in the multigrid config, can
now be bound to only x or y specifically
- add widget for optics-based offset calibration
- use backtracking as method for calculating initial coordinates (instead of
inverting sectormaps)
- some code deduplication between diagnostic dialog and multigrid
- allow to specify matching 'method' (lmdif/jacobian/…) in multigrid config
- can show/hide timestamps in the log window
- make treeview columns user resizable (will be reset whenever the view
changes size)
- simplify stretch logic and remove custom column stretch factors
- minor cleanup for some ColumnInfo definitions

- fix ``ElementList.__contains__``
- show/edit expression field for global variables
- fix SyntaxError on py34
- require cpymad 1.0.0rc2
- use ``e_kin`` only if it was given explicitly when editting beam
- more accurate undo handling for setting *new* parameters
- use space-insensitive string comparison before updating expressions
- fix bug that results in squared UI unit conversion factor during matching
- use the builtin unit conversion mechanism in match widget
- allow overwriting deferred expressions by direct values when editting
- fix for not tracking modifications to element attributes on the undo stack
- fix obsolete checks that would prevent certain updates to element attributes
- simplify and unify ParamTable flavours by relying on model invalidation
- implement "expression deletion" by replacing them with their values
- make "Expression" field immutable for string attributes

- allow negative values in step field (ORM measurement dialog)
- fix AttributeError if using model without undo stack
- fix ValueError for "Add" button in match dialog
- separate "Write strengths" menu item further from "Read strengths"
- add hotkey for "Read strengths"
- find models in breadth-first manner, not depth first
- fix bug that caused incorrect update when changing plot, especially from
plots with many curves to plots with less curves