fixes https://github.com/mitchellkrogza/nginx-ultimate-bad-bot-blocker/issues/51#issuecomment-306734698
fixes a89de5831a (commitcomment-22363496)
globalblacklist.conf is only downloaded if it is a new version.
the version check is limited to 200 bytes of data rate limited @ 5kb.
(this adds curl as a dependency).
adds check_depends() as wget is not installed by default on centos 7
& curl is not installed by default on ubuntu or alpine linux.
adds check_mail_depends() & disables sending an email report if
/usr/bin/mail is not found.
adds a notification for reloading nginx as systemd only writes a
notice to syslog.
adds a note for logging cron to syslog.
adds some ANSI colour to the output.
long options for the command line are removed. getopt is replaced with
the newer getopts (which is compatible with Debian's DASH Shell)
* fixes https://github.com/mitchellkrogza/nginx-ultimate-bad-bot-blocker/issues/35
* adds sanity checks for user command line switches
* adds -v command line option to print blacklist version
