show all matching tracks during test

[simon-weber]

(I could have sworn there was a previous issue for this that I closed.)

The current test ui just shows the first matching track, mostly out of my own laziness. This makes iterating on a playlist definition slow.

In the past I've used https://www.datatables.net to show entire libraries pretty easily. I'm thinking the ux should work something like:

• hit test -> modal pops up all matching tracks (ie, not just those under the limit). tracks excluded by the limit can be distringuished (maybe by color?). This should be noted in the ui.
• default columns are title, artist, album + any columns in the query. other columns are hidden by default, but may be turned on
• sorts applied to the results do not affect the query itself. This should be noted in the ui.
• hopefully the overhead of populating the dom still keeps the test instantish

[simon-weber]

I decided against dynamic enabling of non-involved columns since it looked like a pita, but it might be useful in the future.