[WIP] 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
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.
Note: this is completely untested, contains a lot of TODOs, FIXMEs and
might still break in various places. Basic adding and editing of forms
should work though.