clicking uploads when anon redirects to login (story 359)

* add prepareTemplateUrls function - prepareTemplate is too meaty
* add getLoginUrl method. With $wgMFForceSecureLogin the abstraction seems to be
useful for code reduction
* add getLoginPageHeading to allow customisation of the heading based on the returnto value
* take away can upload check. Firstly this applies to the current wiki so is
wrong when uploads go elsewhere e.g. commons, secondly the page should be visible
to these users (in future we may want to tell them how they can upload)

Change-Id: I28b4b71984928b265fe513b48de1cc36029d76ed
Merge "clicking uploads when anon redirects to login (story 359)"