modified mksconv2 to keep AIRS channel sets unsorted, renamed it
mksconv1, and updated everything downstream.  mksconv1.m could now
be used as a generic AIRS convolver.  Added iasi_params.m to return
IASI user grid params.  Renamed demo1.m to iasi_demo1.m and updated
this to work with new test data.  Updated isclose.m to work with the
signal processing toolbox version of rms.