Move wfMsgExt to wfMessage

* Move wfMsgExt depeciated in MW 1.21 to wfMessage
This should be:

Wfmessage( key, param1 )->rawParams( param2 )->escaped().

This will cause key and param1 to be escaped per Jeroen, and param2 the URL, to be taken as a raw parameter so that it isn't escaped.