Better error messages for service/application creation

[thechinese]

Currently, if you filled out all requiered field, but used incorrect/invalid values, you get a Error Message "An error occured in POST null: Validation Error". This is not very helpful.
The fields with invalid/incorrect values are coloured red, but its only described in the read-the-docs tutorial section , what the exact formatting can be.

Proposal: display the restrictions for the values next to the input field or directly instead of "invalid field"