upgrade link_user_inst_group to first class object inst_membership; upgraded link_eq_item_time_block_group to first class object reservation; inst_group implements linkUser and unlinkUser; fix bug in db_linked when it handles arrays during fetching
user class handles inst_memberships on auth; new inst_group created as needed on auth
Merge branch 'master' of github.com:williamscollege/eqreserve