Initial implementation for interval (#55). Needs a test scheduler...
Added a TestScheduler which collects actions in a queue and has
adjustable time.
Added a unit test. Fixed the implementation. Maybe still a bit naive
when it comes to intervals that are too small to keep up with?
Switched to a default scheduler that actually works together with this
operator.
Fixed indentation.
Fixed yet more indentation issues.
Oops, the test scheduler has to go into the main sources.
Merge pull request #228 from jmhofer/interval

Interval