Remove {Left,Right}Module, as we don't use them.
Move shuffling and sampling into spire.random.Generator.

Previously we had some stand-alone objects but the RNG seemed like a
better place to put these. Of course, methods are still implicitly
added to collections via spire.implicits.

Sampling may be moved out into a type class but for now it will live
in the Generator.
Merge remote-tracking branch 'tixxit/topic/module-simplification' into 2.10.0