keep better track of whether data is climatologies
Use region more in building id - useful for AMWG plot set 13 and others.
Two changes in support of AMWG plot set 13, and other plot sets.
1. use region more in building ids
2. new function reduce_time_space_seasonal_region().  Constrained by a specified season and region,
this will average over all time and space.  Any other axes (two of them in the case of plot set 13)
will be retained.
New plot set, AMWG plot set 13.
Support AMWG plot set 13 by allowing unusual axes (not designated T,X,Y,Z).
support new rectregion class
New file, has a new class rectregion for a rectangular lat-lon region.
This can be used just the same as the list [latmin,latmax,lonmin,lonmax]
but it also carries along a name for the region.
New data type for region.  Formerly it was a 4-element list, now it is an instance
of a class which contains and may be treated as a 4-element list.
Also there is some commented-out code involving vcanvas3.  Uncomment it if you want
to see a plot pop up in a window - useful for testing.
Allow a rectregion object, rather than a region name, to be supplied as the region
in the plot set 13 constructor.
If the table constructor be given a region as an instance of rectregion, treat it the
same as though it were a 4-element list defining lat-lon bounds.