Also add a script that can detect if discovery.xml is no longer in sync
with the core.git filter configuration.
richdocuments.git d6b65b79835bc499f720d15bb6c00441079b2fd6 (Respect WOPI
action names, 2016-10-04) can launch a read-only loleaflet based on this
info.
Change-Id: I09232bb53844d0737dfdc66cd0e87342b9dd0fb6