CMS-4195 Fix initialization-issues

Added start method to initialize repositories if not there
CMS-4198 Improve Context api so that it's easier to integrate with

Using RepositoryId instead of Repository in context
CMS-4198 Improve Context api so that it's easier to integrate with

Removed Context from ContentService and NodeService with friends
CMS-4198 Improve Context api so that it's easier to integrate with

Removed Context from PageService and PageTemplateService with friends
CMS-4198 Improve Context api so that it's easier to integrate with

Removed old Context class
CMS-4198 Improve Context api so that it's easier to integrate with

Renamed new Context2 to Context
CMS-4198 Improve Context api so that it's easier to integrate with

Added tests
CMS-4198 Improve Context api so that it's easier to integrate with

Cleanup after merge