fixed a bug in PDO sending.

now when you send a vector of bytes that's less than 8 bytes long,
it won't send a bunch of garbage at the end of the PDO.
bug fixes to teh CopleyServo class

the most important being initialized variables and switching the pvt
pdo to immediate mode instead of commit on sync. it turns out that
the servos don't like getting a ton of pvt pdo messages that commit
on sync between sync packets. oops.
now the horrifyingly hard coded pvt test works!

make totally sure you never run this on the steering, that would
be bad.