Static attributes which are queried dynamically in flobject.py

Following static attributes are queried dynamically in flobject.py code. These attributes should be added in the static-info and the generated API class definition.

- units-quantity
- file-purpose
- user-creatable?

Start by reading flobject.py and the static-info and generated API class definition referenced in the issue. Trace how units-quantity, file-purpose, and user-creatable? are currently queried dynamically, then verify that each is represented in the static metadata and generated API; the work is done when those attributes no longer require dynamic lookup.

Written by the indexing model from the issue text.