Add LexemeViewFactory to enable adding forms.

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

It also adds a 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
-Remove some css glitches

Bug: T162339
Bug: T162340
Bug: T162341
Change-Id: Ie36d5e5dbd80706f26f91d57abe742decfad3c3d
Depends-On: I41500982409eca564baf9b127e3315983ba26791