Added Javadoc to org.isoblue.isobus.PGN

Minor tweaks were made to the class as well.
Added Javadoc to org.isoblue.isobus.Message

Minor tweaks were made to the class were made as well.
Made libISOBlue demo app keep the screen on.
Added about dialog to libISOBlue demo
Added Javadoc to org.isoblue.isobus.ISOBUSSocket

Minor tweaks were made to the class were made as well