Remove MPController and Tests
Fix for IndexedPiece._import_score()

The method needs tests.
Further Removal of Old MPController
Revert "Fix for IndexedPiece._import_score()"

This reverts commit c8edb3d4191538d17697f182d32b358ae8c72817.

We decided to implement this fix differently; see following commit.
Fix for IndexedPiece.add_data()

This is the conclusion of the previous reversion.

Tests are a little complicated, but forthcoming.