Support profiles for endpoint target base urls

[jhkuperus]

Support switching to complete profiles and editing of single profiles.

Some projects would like to be able to switch the target URL of all endpoints on runtime. This way they can use nocca as a sort of indirection between their system and the target system(s).

To be extra flexible, it should also be adjustable per endpoint.

[KrekkieD]

So basically update the Nocca instance config with a new endpoints object? And wrapping config settings in profiles that can be activated / changed on the fly to update Instance config?

[KrekkieD]

Full config should be based on profiles. This helps with a recording/playback/loadtest profile. Probably best to use a base profile and overwrite parts with the profile-specific configuration.