WIP: use keyword arguments for services

This is mostly a blind conversion. Many scenarios were not tested
(notably, the dns and images services)
The websocket always adds a session: parameter
Also: fix a "message" left behind that caused a syntax error
Merge remote-tracking branch 'origin/master' into keyword_arguments

Conflicts:
	lib/service/dns.rb
Use Combi 0.1.0, required for keyword arguments