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 branch 'interval' into sample
Switched sample from internal clock to using the interval operator
Added a unit test against the sample operator