This adds the microwave tools to GAL in Pcbnew as a new tool:
MICROWAVE_TOOL.
Some new preview items are introduced to support this:
* TWO_POINT_GEOM_MANAGER for managing construction of two-point
geometries, such as that used to construct the inductor.
* CENTRELINE_RECT_ITEM a preview item to draw ractangle with a given
aspect ratio along a line (specified using a TWO_POINT_GEOM_MANAGER)
PCB_TOOL gets a generic event loops which should be useful for more
than just microwave tools:
* doInteractiveItemPlacement() - handles event loops that wait for a
click, create an item on click and then allow moving it
around/flipping, etc.
Fixes: lp:1531323
* https://bugs.launchpad.net/kicad/+bug/1531323
John Beard