allow tmpwatch interval be changed in cron.d config

- move cron job definition to cron.d
- merge cron.daily/{tmpwatch,tmpwatch.directories} to single script
- added trigger to disable jobs if previous version had those %config(noreplace) scripts removed
depend on crondaemon

without it, none of this automatic cleanup would be possible :)
load rc-scripts function library for is_no()
soft dep on cron daemon

see devel-en mailinglist post:
http://lists.pld-linux.org/mailman/pipermail/pld-devel-en/2013-January/023409.html
only valid value for DISABLE_* is yes, no need for rc-scripts for that
allow tmpwatch interval be changed in cron.d config instead of fixed cron.daily schedule