MONIT_CYCLE_TIME environment variable

[Dominic Harkness]

It would be useful to have a MONIT_CYCLE_TIME variable for use with timestamp monitoring on files.

ex. if timestamp > MONIT_CYCLE_TIME then exec "/some/script"

[Tildeslash]

Setting general variables will be added to .monitrc later, which should be used for this. For now please use a number or a template system to set variables in .monitrc