Performance optimizations. Radio no longer automatically powers down.
Radio is now allowed to enter standby. This allows for the removal of
needless delays within the driver. Additional timings optimizations.
If applications desire additional power savings, they should manually
power down the radio as needed.

Multicast write support added.

::write timeout monitoring logic changed to emcompass worst timeouts
for retries/timeouts. Should never trigger anyways...but better safe.

Fixes write retries timeout bug.

Proper hardware delay added to powerUp. Was previously part of
startWrite; which needlessly added overhead to every write/startWrite.

Allows for query of hardware channel.

PA documentation fixes.
Previous commit message applies here.