Work in progress on ResourceLoader mobilification

Work in progress on ResourceLoader mobilification

Goes along with MobileFrontend changes: https://gerrit.wikimedia.org/r/28434

Adds 'targets' option to module definitions, defaulting to 'desktop'.
Only a couple more modules are whitelisted into both desktop and mobile for now.

Startup module takes a 'target' parameter (defaults to 'desktop') to filter
the resource module registration list. Only modules matching the filter get
registered, and thus will be loadable from client-side RL.

Change-Id: Ifb772d4995b8e2ec4b63776fe0bb5b0214f82e04