XML parameters parser extracted to actionpack-xml_parser gem in Rails 4 (#14534).

git-svn-id: http://svn.redmine.org/redmine/trunk@13790 e93f8b46-1217-0410-a6f0-8f06a7374b81
Adds tests for creating an issue with multiple uploads.

git-svn-id: http://svn.redmine.org/redmine/trunk@13791 e93f8b46-1217-0410-a6f0-8f06a7374b81