Implement index meta API

[dkropachev]

APIs to cover:

cass_table_meta_index_by_name
cass_table_meta_index_by_name_n
cass_table_meta_index_count
cass_table_meta_index
cass_index_meta_name
cass_index_meta_type
cass_index_meta_target
cass_index_meta_options
cass_iterator_indexes_from_table_meta
cass_iterator_get_index_meta

[Lorak-mmk]

I edited the description to remove functions that belong to #269. Imo they fit there better.