Validation script
definition of `frontend_links` should be array
Makefile to validate all frontend examples

this relies on tweaking the validation script to guess which schema to use.
Add `clean` target
Rakefile which invokes rspec and then make
Add .ruby-version
Frontend generator removes internal properties

rather than defining the list of allowed properties and removing
everything else, we define a list of 'internal' properties which are
explicitly removed and allow everything else to propogate through to the
frontend schema.
Improve spec wording

this read as though the two things being combined were schemas and
definitions; rather than combining two schemas.