Update markups to be a shared layer with everyone in the fieldmaps group

[RyanBohan]

It would be very useful to have a single shared Markups layer with everyone in the fieldmaps group. 

This way you would easily and automatically see others mark up layers.  Users could quickly see areas that needed increased attention, or areas to avoid ie bees!

Please include a simple filter to only see you own markups, or include others markups.  Ideally with a check box type of filter allowing users to quickly and easily select whos markup they wish to see from the fieldmaps group.

Currently sharing of a Markups layer is static which could lead to problems and confusion with repeated sharing as to what is the latest markup layers, ie Markups, Markups_new, Markups_new_new, Markups_new_new_v2, etc