Add export users as CSV (#218)
Add dates for a few actions, such as active and last execute (run and deployment)
Add attributes to UserView to improve user support
Merge branch 'feature/last-tracker'

Conflicts:
	jar-persistence/src/main/java/com/sixsq/slipstream/persistence/User.java
	jar-persistence/src/main/java/com/sixsq/slipstream/user/UserView.java