Implemented MathParentheses

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Parentheses are now placed when dragging to the screen

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>
Power operations can now also be dragged from the drawer

Signed-off-by: Mark Kamsma <mark@markkamsma.nl>