resourceloader: Remove MW cacheEpoch from module version hash

resourceloader: Remove MW cacheEpoch from module version hash

This seems quite nuclear. I'd actually like to deprecate the
wgCacheEpoch variable more generally in favour of a handful
of more specific version constants, but as starting point,
remove it from the hash used for load.php urls and localStorage
keys.

The latter is also controlled by wgResourceLoaderStorageVersion
already.

Also ref T32956 about a more standalone ResourceLoader.

Change-Id: I913f846090e82d3d822653b9b7ce22233cdb5e90