#84 higher rank support for papco ds

[Reiner H. W. Friedel]

We're starting to use rank 3 data with the papco dataset abstraction, and at least one routine (papco_ds_gridav) not only does not support this rank, but crashes ungracefully when you try to use it with rank-3 data.

Please go through the dataset support routines and make sure that they can all support rank 3 data (time, detector, azimuth, energy) arrays.

[Jeremy Faden]

Note I call that rank 4 data, the time counts too.

[Jeremy Faden]

rank 4 supported in papco_ds_gridavg. added test to tests/papco_lib/dataset/test_papco_ds_gridavg.pro. added keyword /nontick to tests.

[Jeremy Faden]

This is done, by looking for cases where we check the dataset rank and making sure there is code to handle rank 4. Note papco_ds_grid (not papco_ds_gridavg) doesn't handle rank 4 because interpolate doesn't handle 4-D matrices.