Make libmutter and friends parallel installable

In order to minimize the amount of breakage, while at the same time
making it easier to make backward incompatible changes needed to
continue turning libmutter into a capable Wayland compositor, make the
libmutter and friends (libmutter-clutter, libmutter-cogl*) parallel
installable by adding a version number to the name. This changes
various filenames, for example what previously was libmutter.so is now
libmutter-0.so (assuming the version for now is 0), and
libmutter-clutter-1.0.so is now libmutter-clutter-0.so. The pkg-config
filenames and GObject introspection has been renamed to reflect this as
well.

This enables a downstream compositor rely on a specific version of the
libmutter API, while gracefully handling API/ABI changes by having to
update to the new version at their own pace.

https://bugzilla.gnome.org/show_bug.cgi?id=777317