Jeff suggested taking out magic numbers from tree_sortkey tutorial,and explained how to best find the tree_level with tree_sortkey. I putthis into the docs.
making import procs report errors encountered. Making message::register proc throw error if en_US message doesn't already exist. Adding message::revert proc.
leaving sync_time null and not assuming we were ever in sync. This has the downside that we have no base when bootstrapping the new upgrade feature causing a lot of update conflicts. However, it avoids delete conflicts.
