created two helper methods which helps writing unit tests for verifyUpload()
added few more helper methods
first working test, changed helper methods to public because private of course will be ignored by PHPUnit
added more test cases
refactored unit tests
added narrowed list of accepted file extensions and fixed broken unit tests
added new unit test for wrong file extensions
Fixed small typo
Merge pull request #3953 from Wikia/MOB-1886

MOB-1886
Merge branch 'MOB-1785-upload-custom-marker' into MOB-1392-intmap-extension