SW-121. Automated copy of sim firmware files

Automatically copies sim firmware files from openwsn-fw repository
checkout when run a UI with the --sim or --simCount options. Eliminates
requirement to first run 'scons copy-simfw'. However, copy-simfw target
still is available.

Added common SCons script module, site_scons/sconsUtils.py for
copySimfw() since this function is used by both SConstruct and
openVisualizerApp/SConscript.