automount: turn the separated automount binary back into a plugin

It was separated for using only in GNOME fallback mode, but now it's always used in Cinnamon.
Merge branch 'automount-module' of https://github.com/City-busz/cinnamon-settings-daemon into City-busz-automount-module

Conflicts:
	data/org.cinnamon.settings-daemon.plugins.gschema.xml.in.in