Pydm

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* The ability to middle-click a widget to see its channel address works again (Thanks hhslepicka)
* PyDM now strips whitespace from the beginning and end of channel address strings (Thanks hhslepicka)
* Fixed `pydm.utilities.establish_widget_connections`, which never worked due to logic errors.
* Fix a crash in PyDMWaveformPlot when all elements of the waveform data were +inf or -inf. (Thanks hhslepicka)
* Stylesheet properties now properly cascade to child widgets. (Thanks hhslepicka)
* The (always unused) 'channel' property on PyDMImageView has been hidden from Qt Designer (Thanks hhslepicka)
* PyDMLogDisplay now cleans up the log handler when it closes (Thanks hhslepicka)
* Fix a bug in setup.py when loading the requirements.txt file (Thanks hhslepicka)
* requirements.txt has been updated to better separate testing and CI requirements from the core PyDM requirements (Thanks hhslepicka)
* PyDMSliders will no longer crash PyDM if you try to use them without any specified high and low limits. (Thanks ivany4)
* Fix a crash when inserting a tab into PyDMTabWidget in Qt Designer (Thanks ivany4)
* Fix painting bug in PyDMByteWidget (Thanks hhslepicka)
* Hard-coded paths have been removed from some of PyDM's tests (Thanks hhslepicka)


Refactoring
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* Value text formatting (setting precision, setting exponential format, appending unit strings, etc) functionality has now been moved out of PyDMBaseWidget and into its own mixin class. This means that text-formatting properties have been removed from widgets where they aren't relevant.

This release addresses a few small issues:

* Increasing/decreasing font sizes works without needing to refresh the display, and is applied to all widgets, even if they have specified a custom font.
* The pydm.PyQt module has been temporarily re-added. This is intended as a temporary stop-gap to fix crashes for users that have created Display classes that imported from pydm.PyQt. If you currently do this in your displays, please update them to import directly from the 'qtpy' module instead.
* Remove the built-in margins around the PyDMByteWidget. If you need margins around a PyDMByteWidget, you can put it into a layout, or in code, you can manually set them with `PyDMByteWidget.layout().setContentsMargins(left, top, right, bottom)`

======================
PyDM 1.6.4 is another bugfix release.

Bug Fixes
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* EPICS Data Plugins were never sending new value for widgets recently connected.
* Stylesheet was not being applied unless specified using the `--stylesheet` argument. Tests were added to cover also this case. (Thanks mattgibbs)

======================
PyDM 1.6.3 is another bugfix release.

Bug Fixes
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* Base widget rules test was hanging on OSX.
* A ValueError exception was being raised at data plugins when comparing the new value with old value if value was a numpy array.

======================
PyDM 1.6.2 is another bugfix release.

Bug Fixes
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* The middle-click tooltips that show the channel address associated with a widget have been fixed. (Thanks klauer)
* Display classes that don't specify a valid ui_filename no longer cause a crash. (Thanks hhslepicka)
* Widgets that display units or handle precision information will now update properly when the units or precision change. (Thanks hhslepicka)
* In some cases, pyepics and caproto data plugins were incorrectly emitting the 'new value' signal even though the value had not changed. This has been fixed. (Thanks hhslepicka)
* Fix broken unit tests for PyDMSpinbox (Thanks hhslepicka)
* The PyDMWidget event filter (which drives the ability to show custom context menus and middle-click tooltips) is now installed for any QApplication except Qt Designer. Previously, it was only installed for PyDMApplication. (Thanks hhslepicka)
* The PyDM Widget Rules system has been extracted from PyDMApplication into a utility module, allowing the use of widget rules outside of PyDMApplications. (Thanks hhslepicka)
* The PyDMScale widget now has properties for user-configurable limits, and a way to switch between user-configured limits, and limits from the channel. (Thanks hhslepicka)
* The 'Increase/Decrease Font Size' menu items work again. In addition, a 'Default Font Size' menu item has been added to reset the font to its default size.