UsbSerialPort Documentation Fixes

[HTRamsey]

• Documented UnsupportedOperationException for getControlLines
• Minor cleanup of setParameters when unsupported

[kai-morich]

documentation improvements look good, but I intentionally did not add a default implementation to setParameter, to make it obvious that a device typically should implement it, and use UnsupportedOperationException(); only if there is really nothing to set.