Do not overwrite content from community members/bots on re-upload

* Added a method that will check for contributors besides the orginal
  uploader; this relies on an API update in 1.23, query property
  contributors
* The toolset now uses this method to determine if content has been
  added by other contributors or not. if true it will not update
  the wikitext of the mediafile page; otherwise it will.
* Also corrected an issue where a re-upload of a mediafile was
  not being revisioned under the uploader’s user name when run
  from the upload mediafile job.
* Adjusted the explanation next to the Re-upload media from URL
  checkbox

Bug: 63638
Change-Id: I568f8a6ad6ed714db78dc660bfe99716bd896d72