#2475 pngwalk tool with $Y$m$d and $x, and completions case

[Jeremy Faden]

Sadie and I were trying to use the pngwalk to look at some images, and found two problems with the pngwalk tool. (1) Within the pngwalk tool, this completion fails: https://salvatore.physics.uiowa.edu/~iwc/chorus/v6.1.0/rbsp-a_data/2017/12/05/PNGs/,
saying that it is empty. (2) For this aggregation, multiple $x matches for a given $Y$m$dT$H match are not shown, and I believe it just shows the same match over and over. Regardless, the label is just the time, and it should also show the $x part.

[Jeremy Faden]

1. run the script https://github.com/autoplot/dev/blob/master/bugs/sf/2475/createPngWalk.jy
2. point the pngwalk tool at file:///tmp/ap/$Y-$m-$d_$x.png
3. note that $Y$m$d_0 is always shown in the pngwalk.

[Jeremy Faden]

I put in what might be a kludgey solution, but it's fixed.

[Jeremy Faden]

It's tempting that this * should be $(x,name=foo), so that some fields can be ignored.