mainwindow.ui: add Recently Opened action menu
Merge branch 'master' into recently-opened

Conflicts:
	src/ui/mainwindow.ui
Merge branch 'master' into recently-opened
Made recently-opened an actionmenu
Merge branch 'master' into recently-opened
Merge branch 'master' into recently-opened
Somewhat working implementation

Just one thing that need to be fixed:
lastFile depreciated needs to be removed--delegate to recently-opened
when that's fixed it'll probably work the way it's supposed to work
Removed old lastFile functionality replacing with recent files.

Readded Ctrl+Z keyboard shortcut to open the first entry on the recent files.

Fixes #22