Add parameters to shorten uptime display

Ref #316
Update tests
Add timeout to thread join calls to avoid deadlocks
Increase external IP polling interval to 5 minutes
Disable continuous polling of CPU count in load segment
Rename time.py to monotonic.py

This makes it possible to run modules in the lib/ directory standalone.
Merge branch 'feature/shortened-uptime' into develop
Merge branch 'various-improvements' into develop