JS API for dragula moves callback

Problem:

The Drupal.registerLpbMoveError function provides an API for registering functions that are used by dragula's accepts callback to prevent components from being dropped into particular containers.

Similarly, developers should have a way to register functions that are used by dragula's moves callback.

(See https://github.com/bevacqua/dragula for usage of both accepts and moves callbacks.)

Proposed solution:

Modify Drupal.registerLpbMoveError to accept a second parameter, specifying the callback to use (i.e. "accepts" or "moves"), with "accepts" being the default to support backwards compatibility.