Ignore generated string.h
Sane programmers do not pass NULL to deinit
Redefine ws_object_deinit

The function now invokes all the deinitialization callbacks for a type.
Also, it doesn't return anything anymore, since the information is
useless.
Fix tests for ws_object
Fix tests for ws_set
Merge pull request #374 from neithernut/add-commands-missing_gitignore_entry

Ignore generated string.h
Merge pull request #377 from neithernut/mod-objects-deinit

Redefine ws_object_deinit