Description of the new feature/enhancement

Sometimes I like to have my panes organized in a specific way. This can be difficult when you are only allowed to split to the right or below. I suggest adding commands to split above and to the left. I know conemu was capable of splitting panes in any direction.

Proposed technical implementation details (optional)

Add splitUp, splitDown, splitLeft, splitRight commands instead of / in addition to splitHorizontal, splitVertical