Having module definitions living inside SkinMonobook makes them
less discoverable. It also shouldn't be necessary - even if there
are soft dependencies on other modules.
A new file resources/optional-enhancements.js is added which will
load the two optional dependencies based on whether they have been
installed on the client.
Bug: T203023
Change-Id: If9a88db52deb0cc91d58cbb40693d4cd448eabbc
