(core) First stab at Schedules indicating they are done.

Just enough to get everything compiling and all tests passing.  The
Union Schedule still needs work to complete it and tidy it up.
(core) A simple Take Schedule implementation.

Not added to the Schedule testing generators yet, as the Union Schedule
is still broken.
(core) tidy a little
(core) WIP Take spec
(core) tests for the Take Schedule
(core) Smart constructor for a one-off request
(core) Smarten-up layout
(core) Fill in missing implementation of Union
Merge branch 'feature-terminating-schedules'

Conflicts:
	core/src/test/scala/scheduling/CommonGenerators.scala