adds Javascript MAVLink generator
cleanup before issuing pull request
Improves example code in readme
remove copy of jspack lib, add x25crc to core

This removes the static copy of the jspack lib, adding it as an npm dependency.  Also, this removes the stub 'mavutil' object, which only contained the x25crc function, which has been added to the mavlink object.
Generator now creates npm modules for each implementation
improves README to show how to send messages
fixes generator, tests to refactor generated mavlink object
adds tests to cover managing bad packet counts
adds a reference to the connection, so the send function can work
changes how the send() function works to also pack with correct seq#
adds test, code to remove NUL chars from strings
removes spurious logging, modifies unit tests to check for encoding/decoding mav_mode for apm