Improvements in grid columns selection

Upon Ophelien request, you may now filter columns in columns selection popin:

Context

With more and more tags being used, the columns list gets very long.
Adding a filter allows to be quick in selecting what you want to see!

Nice idea :-)

Change

You may now input any string or regular expression in the search input, and only matching columns will appear in the list.

It allows faster selection.

Note that all other columns selection state do not change when filtering.

Improved CSS

On Firefox, the sort icons were not visible because of the elevator appearing on top of them.
I tweaked the CSS to make it work better on Firefox.

That's a pain to have different behavior :-(

I also took the time to increase the icons size for easier access, and I added tooltips.

Cheers! Thibaut