(bug 25339) Allow specifying separate base paths for local and remote paths in Resour...

(bug 25339) Allow specifying separate base paths for local and remote paths in ResourceLoaderFileModule::__construct(). Extensions can use this to properly point the resource loader to their resources in a way that doesn't depend on the extensions/ directory being a subdirectory of phase3/ on the filesystem and that respects $wgExtensionAssetsPath. Also converted all extensions using ResourceLoader to use this approach, except MWEmbed which uses way more indirection building its module registrations than I can deal with after midnight.

What actually happens here
* Add $localBasePath, $remoteBasePath params to the FileModule constructor, defaulting to $IP and $wgScriptPath respectively
* Add getLocalPath() and getRemotePath(), which use this information to build a proper FS or URL path for a file
* Make readScriptFiles() non-static so it can use these functions
* Run every single file path we use through either getLocalPath() or getRemotePath() as appropriate
** Except file dependencies, these are already prefixed. Our inability to give them special treatment caused bugs earlier
* Kill prefixFilePathList() and resolveFilePath(), no longer needed