Bring starcheck characteristics back into the project

The characteristics were broken out into a separate project.  This
commit brings them back into the starcheck project to streamline updates
and improve traceability.
Remove version link strategy from characteristics

Remove the symlinking for fid characteristics and model_spec and
store these as plain/versioned files in the repo.
Merge pull request #65 from sot/bring_back_characteristics

Bring starcheck characteristics back into project