Improve search api

This MR refactors the usage of the sms and cv apis. For each entity there is now an XYZApi class.

All the entity specific api classes are collected in one overall Api class (which also is the only point where the urls for the apis are handled).

And: Via a plugin is the api instance injected in all pages & components, so that it can be used on everywhere easily.

It is best if !24 (merged) is merged before.