The styling for the Edit Columns menu for datagrids resulted in a lot of

unclickable dead space around icons and text, requiring more precise

clicking in order to add or remove columns. Along with this, the

checkmark icons weren't properly aligned and were actually clipped a

bit, based on their position in the spritesheet.
This change tightens up the spacing, removing all the dead space so any

click anywhere on a row will add or remove the column. It also removes

unwanted whitespace before the labels, fixes the referenced position of

the checkmark icon in the spritesheet, and fixes alignment of the icon.
To improve accessibility and to better inform users just a bit, a title

has been given to the row indicating if a click will add or remove the

column.

Checked that there was no longer any dead space within a row.
Checked the title on the cells, icons, and text.
Checked the alignment of the checkmarks and the in-label icons to make

sure things were consistent.
Tested clicking on the checkmark area and the label to make sure

columns were added and removed.