Push more functionality into model.User

[hferentschik]

User has some methods like HasActiveBuilds and HasBuilds, but at the same time we do something like this in conditions:

u.DoneBuild.Status.CompletionTimestamp.Time.Add(c.idleAfter).Before(time.Now()) 

It would be nice to pull this into the User. Something like LastestBuildCompletionOlderThanIdleTime(idleTime).

Similar:

 b.JenkinsLastUpdate.Add(c.idleAfter).Before(time.Now()) 

This should also allow to add some unit tests around these conditions.

[hferentschik]

This issue relates to issue #143 and I think we need to restructure the whole model.User struct. We should be able to keep actually lest state than we do right now. In terms of the Idler, we don't need all the information we try to keep track of and there is a risk that is gets outdated.

[hferentschik]

Closing this issue in favour of #143 which also will entail a rewrite/change of model.User.