HG-195 rename global namespace to Mercury & Mercury.Utils alias to M

The way we currently implement ads in Mercury revealed a problematic issue with module inclusion. Ads code basically imports a package of assets from the legacy Wikia/app and those modules (cookie, geo, etc..,) all abuse the global Wikia namespace, occupying namespaces even when AMD is used. This resulted in pollution in our namespace. To remedy this, I've renamed our namespace to: `Mercury` and the `M` (the alias to Mercury.Utils).

This PR includes all updates to the code base & tests.