Add LexemeViewFactory to enable adding forms.

This adds a LexemeViewFactory extending ControllerViewFactory in order
to wire the lexemeview, lexemeformlistview and lexemeformview
together including toolbar and ToolbarViewController for the
lexemeformview.

It also adds an intial LexemeForm model for the datamodel frontend
which at the moment does not inherit from Entity. It is only needed to
provide the equals-method for the ToolbarControllerView.

Persistence is not implemented yet. It uses a fake model instead of an
EntityChanger that always resolves the "save" promise.

TODO:
-Write tests for lexemeformlistview and lexeformview

Bug: T162339
Bug: T162340
Bug: T162341
Change-Id: Ie36d5e5dbd80706f26f91d57abe742decfad3c3d