Nionui

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- Add ability to set color/font/word_wrap on declarative UI labels.
- Enable strict typing on entire library.
- Drop support for Python 3.7, enable support for Python 3.10.
- Add methods to create persistent value models.
- Allow subclasses to override persistent value behavior.
- Configure stack widgets to expand/contract as content changes.
- Fix issue with declarative label width.
- Extend declarative components to make it easier to implement all-in-one handler+view.
- Improve handling of focus in dock widgets.
- Add divider and draw canvas items and declarative divider.
- Standardize to use a single event loop managed by Application.
- Add canvas item slider.

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- Fix radio button grouping issue.
- Improve font scaling behavior on Windows when running PyQt or PySide.
- Add a window.activate method.
- Expand action capabilities and be able to match key sequences.
- Add additional border color support for declarative images.
- Add icon based declarative radio buttons.
- Fix issue with lists making the selection visible.
- Remove menus from utility windows (affects Windows and Linux).
- Fix case of preference dialog when no preference panels are registered.

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- Default SVG now uses fastest compression rather than best (see nionswift-642).

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- Fix some drawing inconsistencies during splitter dragging.
- Minor improvements to drawing performance.
- Fix potential crash when closing canvas items with threads.
- Add window file path support to Window.
- Add support for directly getting last or current keyboard modifiers.
- Only change canvas item focus when no key modifiers are enabled.
- Add menu methods for adding only if enabled and checking if enabled.
- Expand action architecture to support parameters and results.
- Require sizing to be set by the canvas item (backwards incompatible).

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- Add color dialog support, a color well widget, and some color utility functions.

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- Execute context menus actions by queue to fix crashes.