This renames some APIs from Efl.Pack in order to try and
make them more sensible. Feedback welcome.
Also, most APIs now return bool, where false is quite unlikely
to happen.
This moves the part_box and part_table APIs to a fake object
like was done in Edje Object.
This also adds support a few new APIs to those containers,
so they behave exactly like Edje.Object.
This is another implementation bit of "eo_part".