Check userCanUpload when wgMFPhotoUploadEndpoint is set

* Move logic to check if the user is allowed to upload in MobileFrontend
complete to MobileContext. SpecialUploads and the sidebar now using the
same rules.

* If wgMFPhotoUploadEndpoint is set, check if the user is allowed to
upload, too.

Follow up: I35804a6a56a2885d6ff00df70c38c3b469150899

Bug: 62598
Bug: 68375
Change-Id: Ic2bd936d1a7a25a5845f5b18378d6092e0d0f291
Merge "Check userCanUpload when wgMFPhotoUploadEndpoint is set"