Add service to dump VP geometry for use in Allen

The same information is needed as is used to obtain conditions in PrPixel. To avoid code duplication, two files have been moved from Pr/PrPixel to public headers and the linker library in Det/VPDet in LHCb!1884 (merged).

Test has been updated and passes.

FYI @clemenci as author of VPGeometry.{h,cpp}; @rquaglia @sponce as frequent contributors to Pr/PrPixel