Finally solve the bug on Samsung Android 9 and 10 phones that the Dialogs Main & patterns wouldn't be modeless: move the setting of this flag earlier, to the 'onCreateDialog()' function.
Minor.
Only 2 dialogs are modeless now: MAIN & PATTERNS
Move to AndroidX, target API level 29.
(Hopefully) make the Dialogs NOT disappear on clicks outside (previously this wasn't working on Android 9).Lower API requirements to 21.
More support for the 3x3x3 Solver: more of the actual 3x3x3 solver mechanism.