fix #6585 scan_id is searchable, added individual field search

[moellep]

• fix search for specific field #6581 and fix Add FLASH to sirepo.lib.Importer #6420 search for a specific field
• fix raydata: column to add should be pulled from all visible scans #6191 column list refreshed from each scan result

[moellep]

@e-carlin and @rorour please give this a test (searching, column selection, pdf download). I refactored the client quite a bit and could have introduced new bugs.

[rorour]

• "Search Text" is case insensitive but search text in individual fields are not
• The box for the "Select Search Field" dropdown is very wide. Not sure if it needs to be this wide to accommodate some long field names, but for the longest one I saw (OAV_resolution [um_pixel]) it was still almost twice as wide as it needs to be.
• Functionally, the "Add Column" dropdown is a big improvement, but visually, the button looked a lot cleaner. Making the text bold might look better, and maybe you could also make it less wide (tighter around the "Add Column" text) since the field names don't actually appear in that box when selected.