Switch to Java Simple Serial Connector, a replacement for RXTX

Switch from RXTX to JSSC https://code.google.com/p/java-simple-serial-connector/
Java Simple Serial Connector is a multiplatform java + native code library aiming at replacing RXTX.
A variety of benefits have been observed so far in using JSSC instead of RXTX, the most important one being stability.

Further testing with all operating systems is needed.