[api] fix request schema

grouped can appear more than once, but it always has one id

This left unnoticed, as request/show did not validate due to the usage of
send_data, which is now fixed. Also avoiding double render errors if an
exception happens
[webui] do not simply reset the cache but also write it to the backend

Really fixes #485
[api] add more features to the request RNG

I also added a test case to check our existant schema - to great horror
it's all failing -> issue #489
[api] fix TODOed test case for code quality
[activexml] remove method_missing to ease debugging

This catch all makes it very hard
[webui] remove webui_package model in favor package