Magic Cube

Improve the About dialog.

1) Relax requirements as to OpenGL ES ( now only 3.0 required )
2) fix a crash in Solving state

(Hopefully) make the Dialogs NOT disappear on clicks outside (previously this wasn't working on Android 9).
Lower API requirements to 21.

Minor tweaks to the 'Prev' buton in Solving state;
Relax requirements in the Manifest - now only 'android.hardware.faketouch' supporting device is required, i.e. something that supports basic point-click-drag-unclick. No need for full 'android.hardware.touchscreen' thing with its multitouch silliness.

Minor.

Add a 'withdraw move' button to the Solving UI state.

Bugfix

Minor

Make chances to randimoze a given row when scrambling dependant on the type of Object.

The point: in case of the Cube, all rows should have equal chances. In case of the Pyraminx, the smaller the row, the smaller the chance should be. In particular the trivial 4 corners of the tetraherdon should have a very small chance to be selected.

Bugfix.