Added ability to turn some builtin tracing events off

[shuhaowu]

CyclicThread::Loop, CyclicThread::Sleep can be selectively turned on and off for tracing.

Also added ability to trace the CyclicThread::Sleep and also send InstantEvent if the Loop overruns, which allows for easier visualization.

Fixes #45

TODO:

• [x] Test instant event
• [x] Test turning on off stuff
• [ ] Investigate variant instead of the nullptr trick for performance.