Quick-fit mount plate for PrintrBot extruder

*Work in progress*: Printed but not tested.

Working to convert my PrintrBot Simple 2014.1 Maker Edition to RichRaps Quick-Fit system, so I can use Bowden most of time - but with possibility of direct extruder for NinjaFlex or other more exotic extuders.

Note: the hotend is in lower-right corner instead of middle as is typical. This to keep the original position.