smurf: Allow makemap to export compressed NOI model

Since skyloop is to support noi.box_size, it will need to cache the NOI
model created by the first invocation of makemap. But this could be
another fill size time-series data set since previously the NOI model
could only be exprted as the Variance component of the RES model. Now, by
setting noi.export, the NOI model can be exported in compressed form
(i.e. only one value per noi.box_size time slices of raw data), without
lots of unneeded extras like quality and residuals, etc.

, but this