Return more errors instead of panic

[DerInti]

Hi,

I use this module in an Prometheus Exporter for Fritzboxes and it works like a charm - but yields a panic in case of the tyniest unexpected situation. This is a take to react to failures when utilizing the library.

I have changed some minor stuff which should be kept apart by the different commits.

• I just had to rename the module from gofitz to gofritz
• the service-description of Fritzbox 7590 Rev. 1 is added
• the codegen should not fail anymore, because of a missing stub (functions_register_test)
• Errorhandling in the stub-template and most of the soap functions

‼️No generated code is committed.

[nitram509]

Thank you very much for your contribution 🚀

I will merge it straight and re-run the code generator (which needs some love first).