Update rethinkdb_spec.cs for RethinkDB 1.5

Also add regenerate_rethinkdb_spec.sh file to give some hints to anyone
trying to perform this regeneration in the future.
IndexCreateQuery
Add IndexList query
Add IndexDropQuery
Add GetAll query
Add support for secondary index in Between()

Addition of TKey as a parameter to Between also opens the door for an
easy implementation of Expression<Func<TKey>> leftKey & rightKey, but
I haven't implemented those right now.
Add support for secondary indexes in EqJoin()
Merge pull request #97 from mfenniak/issue_97

Support secondary indexes