adding output with timestamp for all reports

Actually, check_urls.sh is returning .log and .json files. These files should be kept in workdir, except when the init argument is used. Then, to be able to keep the history of scans, adding a timestamp before the filename would be useful. Eg : YYYYMMDD_hhmm_<result_name>.{log,json}.

Same behaviour should be used for check_certs.sh Actually, it just produces output on stdout.

However, for users who wish to use it through a daemon, it would be more suitable to write results in /var/log in a single file for each script (not a new file for each analyses)...

Another option would be to store results in a json compliant database, like elasticsearch or MongoDB, but it seems to be a bit overkill for now...