Save a timestamp of the last action to firebase
Save a timestamp of the last action to firebase

Every action the user takes will now save a timestamp to Firebase, in
a new property `stateMeta`, designed to hold the data that does not make
up a user's loadable state.

This data will allow the Dashboard to show what users are currently
active.
concord-consortium/geniblocks,concord-consortium/geniblocks,concord-consortium/geniblocks