removed snapdate and snapshotid params from getPkgs, now lookup snapshotid in options set earlier
added param to getsnapshotid to force using most recent of a date if more than one avail
small typo fix in mran_set
updated docs for rrt fxn, fixed internal snapshotdate param refernce in call to rrt_init and rrt_refresh
added two helper fxns get_snapshot_date and set_snapshot_date for determing snapshot date to use
using new approach to setting snapshot date