introducing FOUND flag for each network and remove all networks that were not found;
this fixes a bug that disappearing networks were not detected;
made output a tiny bit nicer
- writing log to file instead of STDOUT
- added timestamp each line of output
- quoting each '"' and ";" of the SSID with a '\' to format CSV correctly
not using [] for timestamp any more to generate valid CSV
writing also messages into own file
added path of script to data files to allow it to be run from a user cron job
- do not suppress stderr output of iwlist
- using absolute path for iwlist command