Refactoring & tidying of much of the serial por

 * If port not found, switching back to error.
   Since the change was made so long ago I am hoping we can go
   back to having this useful descriptive error.  It's really
   nice to be reminded when the port setting may have remained
   from a previous project/setup.

 * Also refactor and extract methods in the ArduinoSerial class for
   clarity.

 * Also renamed variables and method names to be consistent with
   Java standards.
Merge branch 'refactoring' of github.com:kigster/arduino-eclipse-plugin into refactoring