rename MediaCore's 'jwplayer.js' to 'jwplayer_.js'.

JW Player 6 scans all script tags to check for a referenced 'jwplayer.js' file and will just take the first one to load other resources (jwplayer.flash.swf, jwplayer.html5.js).

Without this change JW Player 6+ won't start in JS debug mode ('?debug=True') mode.
extract fake request building into a plain function so it can be used also outside of tests (most notably when building the Sphinx docs)
move common environment/request setup functionality into mediacore.lib.test.support
fake requests should also set up a basic translator
export 'StorageURI' from mediacore.lib.storage so we have a unified API and all storage-related class are available from that module
use test support functionality to set up a dummy Pylons environment/request to build the documentation.

This also removes the necessity of editing the SQLAlchemy url in development.ini just to build the docs without DB interaction.
update InterSphinx URLs