Madgui

- element info box: add UI to switch element
- floor plan: support 3D models (no more curved sbends anymore though…)
- floor plan: add UI to change view perspective
- floor plan: fix mirror inversion
- main/plot window: set window title
- main window: add config setting for initial position
- codebase: unify the workspace/segment mess, now only have 'model' again
(it's unlikely that we will ever be able to work on less/more than one
sequence in the same workspace anyway)

bugfixes:

- fix for missing setObsolete on Qt<5.9 (was previously fixed only partially)
- fix empty list of optic elements in output file
- fix beamoptikdll not initiating device download due to flooding
- fix duplicate value bug in the readout logic
- decrease chance of race condition leading to inconsistent readouts

UX improvements:

- log to main logwindow as well
- increase logging verbosity during orbit response measurements
- flush file after each write
- vary steerers in sequence order
- avoid one redundant readout
- increase default steerer variation to 0.2 mrad

ORM analysis:

- handle missing ORM entries as zero
- restrict to used knobs
- fix empty steerers field in record file
- handle accumulated errors in ORM analysis
- add simple plotting script

- Update the User Guide. Work in progress
- Add dynamical color to snapshots

- fix RecursionError in ``UndoStack.macro()``, that occurs e.g. when using
the MATCH/sectormap methods of corrector dialog
- fix potential NameError in ``UndoStack.rollback()``
- fix unwanted signal connections that can lead to TypeErrors and multiple
signal handler executions (e.g. triggering the EditConfigDialog twice)

- remove ``api_version`` entry from model files
- add menu item to load MAD-X file
- autoscale plots when pressing "Home" button
- add shortcut method ``model.sectormap`` for use in ipython shell

- twiss/beam init dialog:
- remove menuitems for separate init tabs, move to file menu
- treat attributes specified in the config as reals, not ints
- update enabled-state of save/open buttons according to current widget

- element infobox:
- add tab with sectormap for element infobox
- update title clicking on another element (previously was updated only
when changing using the combobox)
- fix "open" button

- both:
- use spinbox=true by default
- use QuantityValue for floats (spin to win!)
- fix editting bool values
- fix display bug when showing SpinBox for IntValue
- fix "save" button

- matching:
- match against variables inside expressions
- reuse computed init conditions after applying corrections

- internal resource handling:
- remove PackageResource
- replace pkg_resources with importlib_resources where appropriate
- remove madgui.resource package

- ellipses plots:
- add ellipse tab for init dialog
- add x/y labels
- use tight_layout
- use ui units
- draw ellipse over grid
- fix swapped ellipse axes when alpha is negative
- fix swapped formulas for the half axes

- units:
- pass values internally as plain floats, convert only for IO/UI (2)
- Replace all Expression instances by their values, get rid of
SymbolicValue
- introduce globals for ``madx_units`` and ``ui_units`` used for
conversion
- format degrees with "°" symbol
- improve unit labels for lists
- remove pint units file, use the default one shipped with pint instead

- revisit auto load model feature
- auto loading was subtituted by a button in the read strengths dialog
- updating pyqtconsole dependency to 1.1.5