SearchHighlight performance on large dataset

[byxworm]

Hi.

It seems, that change with columns highlight (#287) cause full highlights redraw for each column on table search, which lead to performance issue on large data set.

You can compare page freeze time on each key press in search field in previous and current plugin version.
Previous plugin version: https://jsfiddle.net/mqj9Lacf/
Current plugin version: https://jsfiddle.net/ckdhtLnv/6/