A combination of factors caused inconsistent button movements when using the arrow buttons to move it, namely floating point approximation and the round down performed when snapping a button to the grid. Sometimes the layman solution is the best one: adding/subtracting one to the move amount depending on the direction ensures that the button always ends up on a grid line.
An unusual big commit, unfortunately needed because none of these changes would make sense nor work individual. A quick list of what have been done follows.
* Introduced a control panel to control buttons replacing the FAB bar
* `ConfigurableButton` and `OnScreenConfiguration` interfaces have been introduced to allow for easier proxying of actions when applying the same changes to all buttons
* Button resize logic has been stripped from the buttons in favor of the new sliders
* General cleanup and renaming of various methods to better reflect their functionality
The layout preview/editor doesn't instantiate an Application instance, therefore accessing `displayMetrics` from the app context would lead to a crash, and the view being mocked in the preview.
Additionally a default grid value is defined for `AlignmentGridView` to avoid a crash because of an invalid iteration step in the drawing loop.
As part of this commit, a `defaultEnabled` property was added to `OnScreenButton` to determine the default visibility of buttons. This is required because L3 and R3 should be hidden by default and only enabled by the user on demand.
Additionally, the buttons' mask values were added to `ButtonId` members, as adding entries in the middle of the class conflicted with the `ordinal` enum property, making it unfit to use for our purposes.
Finally, the `ControllerType` class was extended with an array of optional buttons. Optional buttons represent buttons that are allowed to be displayed on screen, but shouldn't be included in the controller mapping activity.
Edit mode configuration parameters are now shared between the view and the buttons in a small `OnScreenEditInfo` object, avoiding variable duplication about edit state. The `editingTouchHandler` has also been simplified to only lookup the button if one wasn't being edited already.
`PreferenceDialogFragment`s have been extended to use `MaterialAlertDialogBuilder`, which results in Material Design 3 dialogs. `DialogFragment` creation logic has been moved to `SettingsActivity` to reduce code duplication.
