Added cropplans and ricestageplans globals

These contain lists of cropping plan parameters that had been specified
in procedures cropplan and ricestageplan.
Replaced cropplan, ricestageplan with simpler versions

These set the cropplan and ricestage in a subak.
ricestage is only called in setup.
The old versions each defined 21 variables and chose one of them.
The new versions use the new globals cropplans and ricestageplans,
and does a two-stage index into them to get the appropriate values.
(I think that Janssen hadn't yet realized that NetLogo could handle
lists of lists, or maybe he didn't like such constructs.)