Comment out debug statements with console.log().
Comment out another debug statement.
Added a keysuffix to the form_key so that storing data for Case Activities does
not mix data from different cases (for situations such as Case Activities where
not all form fields are filled-in: restoring would restore data from a previously
loaded case activity form, very annoying for large forms).

Also added ways to deal with a full localStorage (catch the exception):

* it flushes all the localStorage
* informs the user about the full storage
* and if the user deletes manually for a given Entity (ex: Activity), it deletes
  all stored fields for that given entity and ignores the keysuffix.