Added service.tags command
Added service.tags testcase, and it passes
Updated ChangeLog
Eliminated START_PENDING from service state machine

On a service start, the service state machine used to transition
to SERVICE_STATE_START_PENDING and then to SERVICE_STATE_START,
but there really wasn't much point in that because both states
looked the same in the event, and used the same logic to decide
when to restart.

This simplifies the code a bit.
Removed unused service state SERVICE_STATE_ALLOC_CTL
Implemented cancellation of service.start

Using "service.start NAME -" you can now cancel a scheduled
service.start.

Also fixed bugs which had broken the delayed-start feature
and rendered it unusable in the first place.

Updated docs and added test case.

fixes #41