Use localStorage to save user generated morph forms

When a user creates a new form, we save it now in localStorage. This way he only has to add an analysis once in his life (or as long the localStorage cache is not cleaned).

This is slightly problematic when using different morph configuration though (something we don't do yet). We might want to make this more robust in the future, but could be a case of YAGNI, as this is a temporary feature also.

By using localStorage we can also prototype the lexical inventory functionalities of the future!