Added some javadoc
Added JodaTime dependency
[JENKINS-21267] Adding tooltip to show remaining time
until next build.

E.g.: in 2d 1h 3m
[JENKINS-21267] Added method to obtain the remaining time.
Added some javadoc
Merge branch 'JENKINS-21267'

Conflicts:
	src/main/resources/hudson/plugins/nextexecutions/NextExecutionsWidget/index.jelly