Distorted Android

1) add missing call to BlockController.onPause() / onResume() to the Tutorial activity
2) rearrange BlockController's error reporting to make the case where the MessageSender thread has died separate
3) in such case, resurrect the thread
4) simplify and harden the EffectMessageSender

More debugs to the EffectMessageSender.

Firebase shows that we have a problem when an app is rapidly restarted, i.e. when is it paused and resumes within tens of milliseconds. Then sometimes the EffectMessageSender thread dies.

Attempt to limit this by synchronizing the whole 'start' and 'stop' methods, although I suspect this will still happen because the very methods are probably in such case called in the wrong order.

Some more debugs for the case when the UI is blocked.

Minor.

Convert the Ivy corner cubit to the new, 'universal' cubit creation method.

This forces deep changes to 'createRoundSolid' and the underlying 'MeshPolygon' class to make them support arbitrary Polygon 'centers of face convexity'.

Reason: the faces of this cubit are concave and such default 'center of face convexity' (which by default used to be (0,0)) turned to lie outside the face - which produces strange visual artifacts.

Copy constructors for the Statics.

Dynamics: minor.

Dynamics: consolidation of code.

Dynamics: introduce two speed modes - smooth and segment_constant.
Prepare the third mode - globally_constant.