config_files:convert_crontab now allows MAILTO

No longer have to manually edit the crontab as MAILTO can be specified
when generating the file.
Minor example code formatting
Remove unused cron example variable

Not used in config/crontab-example.ugly
Update cron variables documentation
Remove superfluous crontab docs
Generate crontab to /etc/cron.d/

Might as well put it in the right place
Use better default for VHOST_DIR in cron example
Add better sections to crontab and init setup
Add better examples for generating the alert daemon
Add variables for purge varnish init script
Minor updates to init script setup
Merge branch 'gh-pages-crontab-setup' into gh-pages