reflection support for contacts

[kecnry]

Reflection support is currently implemented in phoebe-lib and has been incorporated into the backend but still needs thorough testing.

• [2.0b] test reflection vs legacy (now PASS, see reflection nosetest fails #39)
• [oc support] backend support for overcontacts (already exists in libphoebe)

[kecnry]

reflection nosetests now pass (see #39), so moving milestone to oc support

[horvatm]

This should work with general reflection routines, not for n-convex-bodies. I don't know how far is the logic outside libphoebe to handle this.

[kecnry]

this should be implemented, but I don't know how well its been tested. We need to write a test (preferably nosetest) for this.