Implemented 'go to all build files' (U).
Renamed session variable.

OLD: Session.is_backtracking_to_score_manager.

NEW: Session.is_backtracking_to_abjad_ide.
Renamed session variables.

OLD: Session.is_navigating_to_score_(materials, build files, etc).

NEW: Session.is_navigating_to_(materials, build files, etc).
Wrote (U) tests.
Wrote (D) tests. MILESTONE.

MILESTONE: 1000+ tests.

There are now 1010 IDE tests.
Wrote (K), (M), (G) and (Y) tests.
Wrote (**) tests.

Tests make sure you can use (**) to go to library from anywhere in IDE.
Renamed session variables.

OLD: Session.is_navigating_to_score_(foo).

NEW: Session.is_navigating_to_(foo).
Renamed session variable.

OLD: Session.is_backtracking_to_abjad_ide.

NEW: Session.is_navigating_to_scores.
Wrote navigation tests from (**) to (U), (D), (K), (M), (G), (S), (Y).
Wrote (**) to (**) navigation tests.

The (**) command no longer functions as a toggle.

Use (**) to go to the library. Use (S) to go to scores.
Added ScoreInternalAssetController.

The class is currently a stub.
Integrated ScoreInternalAssetController.

The primary goal has to do with the extremely global view provided by (**).
When in (**) the (Y) command should be available (to view all stylesheets) but
the (y) command (to view stylesheets in a single score) should not be
available.