Move event editor into its own source unit

The event editor was growing into a big boy and deserves its own
source unit for better organization.  The classes/filenames have
better names now and the .ui files are renamed to match their classes.
Rename .ui files to match their composite class names
Refinements to Toolkit.Deck/Toolkit.Card
Merge branch 'master' into wip/734698-agenda

Conflicts:
	po/POTFILES.in
	src/Makefile.am
	src/california-resources.xml