Continued with adding features:

Continued with adding features:
- merged add_user into list_user as other admin pages are constructed same way
- introduced mobile selection "box" template with target controller to not have the same form all over again
- added both regular and administrative controller with interface for administrative functionality for mobile providers
- rewrote try-catch block: only the actual method call that throws the checked exception should be included in the try block
- return actual list and not an unmodifiable version
- added templates for list/edit/delete mobile providers (admin area)
- listing of mobile providers should be okay now ("basicly finished")
- renamed variable to make it more clear (mobile provider)
- adding new mobile providers "basicly finished", still some improvements (avoid ugly exception output) may be required
- added a lot new language strings + removed "add_user" from merger

Signed-off-by: Roland Häder <roland@mxchange.org>