Delay adding most recent exclude string

[elliotjo]

As you type a string into exclude line edit, anything that matches will immediately disappear. This requires the user can mentally remember the exact string that is trying to be excluded. It might to change the behavior to help the user. One possibility would be to make the "current string" (the one that the cursor is in) highlight matching parts of logs instead of excluding them. The string would become an active filter once the user moves to the next string, or moves focus to another control.