Do not exclude Documentation from applications

There is currently no way of launching the desktop-wide help other
then running yelp explicitly from the run dialog or a terminal. It
should instead be included with the rest of applications.

https://bugzilla.gnome.org/show_bug.cgi?id=622458

data/gs-applications.menu

@@ -32,7 +32,10 @@
 		<OnlyUnallocated/>
 		<Include>
 			<And>
+				<Or>
+					<Category>Documentation</Category>
 					<Not><Category>Core</Category></Not>
+				</Or>
 				<Not><Category>Settings</Category></Not>
 				<Not><Category>Screensaver</Category></Not>
 			</And>