Remove redundant boost dependencies
When a new window is opened, don't create an empty document by default, instead display a nice message. When the last document is closed, redisplay that message
Break out the coverage file lookup code
Merge branch 'master' into watch-coverage-file

Conflicts:
	CMakeLists.txt
Merge remote-tracking branch 'origin/no-open-files' into watch-coverage-file

Conflicts:
	CMakeLists.txt
	data/ui/delimit.glade
Only construct coverage instances once per document and connect to the updated signal