#1 Allow period to be in minutes

[Tim Siegel]

This patch changes the way a period is specified, so
that one can
have wrep perform a task every minute, instead of just
once a day. The period specification is now a string
instead of just a number. The string looks like
"2d3h45m", which does the obvious 2 days, 3 hours, 45
minutes.

[Tim Siegel]

period-granularity patch