Fixed issue in live model where a tool was sent a mouse pressed event
each time a mouse button was pressed. Now, a tool is only sent a mouse
pressed event in case the particular button being pressed hasn't
previously been pressed during the current "tool application session".

Added rollback support for bound change tools (edit- and scale tool).

Signed-off-by: Jakob Brandsborg Ehmsen <jakobehmsen.github@gmail.com>