This makes "rotate" into two separate TOOL_EVENTs, which each have a
"multiplier" parameter.
Also added is a namespace for 'free functions' that use TOOL_EVENT
public interfaces (perhaps with other inputs too) to centralise some
decision-making and calculations.
Fixes: lp:1660731
* https://bugs.launchpad.net/kicad/+bug/1660731
John Beard