fix: more supported cron values

[shreddedbacon]

The old crontab generator just passed through values for day and month:

build-deploy-tool/legacy/scripts/convert-crontab.sh

Lines 90 to 95 in a4fc0b3

	elif [ "$index" = "3" ]; then
	MONTHS=$piece
	# Day of Week
	elif [ "$index" = "4" ]; then
	DAY_WEEK="$piece"

while the new cron validates them.

Some values were not included in the validations, this PR addresses those.

http://man.he.net/man5/crontab

       # Example of job definition:
       # .---------------- minute (0 - 59)
       # |  .------------- hour (0 - 23)
       # |  |  .---------- day of month (1 - 31)
       # |  |  |  .------- month (1 - 12) OR jan,feb,mar,apr ...
       # |  |  |  |  .---- day of week (0 - 6) (Sunday=0 or 7) OR sun,mon,tue,wed,thu,fri,sat
       # |  |  |  |  |