smurf: Rename jsasplit as jsadicer

This is so that I can add a new command called jsasplit that does the
reprojection as well as the dicing.
smurf: Add new command jsasplit

A python script that resamples an NDF onto the JSA all sky pixel grid
and then dices it up into tiles.
smurf: Allow jsajoin to be used with non-JCMT data

So you can split a non-JCMT NDF using jsasplit and then join the tiles back
together again with jsajoin.