param: make "param set NAME" show a parameter

makes for faster interaction for show then set
fence: now using MAV_SYS_STATUS_GEOFENCE to track fence state.
fence: can now enable/disable fence from GCS.
fence: now outputs color-coded fence status to console status
Use a more current documentation link: http://tridge.github.io/MAVProxy/
devel: Install a dumpstacks handler on SIGQUIT

If you send QUIT to Mavproxy it will dump stack traces on all threads.
modules: refactor to base modules on a WPModule baseclass

Updates are included for all modules of this package.