Fix OSCAL profile metaschema discrepancy in code generation

[anweiss]

Due to usnistgov/OSCAL#287, the profile types that we're generating from the metaschema don't match those of the actual profile examples. We should implement a temporary workaround in the metaschema generation process until this is addressed in the upstream.

[anweiss]

Workaround has been implemented via #40 but will keep this issue open until usnistgov/OSCAL#287 is addressed.