Add fileprg tests for collections

FilePostRedirectGet plugin is working for forms as long no complex structures like collections are used.

If so, the arrays get mangled. Included is a patch testing for this problem.

Current tests use collections with files and text-fields.

See https://github.com/zendframework/zf2/pull/5244 
See https://github.com/zendframework/zf2/issues/4974

Test fails on current master which is expected due to wrong collection handling.