ENH: Filter testing modules in module list depending on DeveloperMode

In the module selector only show modules in Testing category if DeveloperMode is enabled in application settings
Fixes http://www.na-mic.org/Bug/view.php?id=3903


git-svn-id: http://svn.slicer.org/Slicer4/trunk@23802 3bd1e089-480b-0410-8dfb-8563597acbee