Ogmo 3.4.0 support

[suchipi]

Ogmo 3.4.0 came out earlier this month, and it includes some new features that we should support and some bugfixes. Notably, we should find "filepath" fields on entities and emit them in the build with URLs, and we should change the hardcoded angle units, since they fixed that bug.

To make sure we don't break existing Ogmo projects, we should check the version in the ogmo files and use the existing angle units if it's below 3.4.0.