RL or nothing (story 393 - stable)

1) simplify MobileFrontend to have 2 modes - one ResourceLoader mode
and 1 where no javascript is run at all

2) allow modules to declare mobiletargets

this cleans up SkinMobile.php so that modules are selected based on
whether 'mobile' is in their targets and they have a relevant
'mobiletargets' set.

mobile targets:
alpha: load for alpha
beta: load for beta
stable: load on mobile

3) Deprecate mwMobileFrontendConfig.messages

4) Make MFResourceLoaderModule target mobile

Note FIXME: we should be able to use $out->makeResourceLoaderLink in future rather
than $skin->resourceLoaderLink with some changes to core

Change-Id: I933fd2973d30f62d3ab8f6d2ac145581fa3a2960
Merge "RL or nothing (story 393 - stable)"