show & hide the box around the current line depending on CodeEditorControl focus state

[minesworld]

Or at least an option to enable that.

If there are many CodeEditorControl on the screen only one can be in focus and the text of the others doesn't look so nice if the unnecessary box is shown.

[BreeceW]

This can be configured by setting EditorControl.Editor.CaretLineVisibleAlways = false;