This PR gives the Notifier HAL thread RT priority 40 in RobotBase after
HAL initialization and before the user code is run. This drastically
improves scheduling jitter for TimedRobot's AddPeriodic() functions (in
3512's experience).
It's too risky to set user code as RT because badly behaved code
will lock up the Rio (potentially requiring safe mode to recover).
This needs the user program to be setuid admin to succeed.
The ranges and which value was specified as highest were incorrect on
some of them. On Linux, the range is 1 to 99 with 99 being highest.
From `man 7 sched`:
```
Processes scheduled under one of the real-time policies (SCHED_FIFO,
SCHED_RR) have a sched_priority value in the range 1 (low) to 99 (high).
```
Also clean up the relevant javadoc and doxygen comments.
The old headers were moved into folders because doing so avoids polluting
the system include directories.
Folder names were also normalized to lowercase.
