sTgcDigitization - Add conditions algorithm to load efficiencies & use the detector manager from the conditions store

• Write database infrastructure to tune the sTgc efficiencies via external efficiency numbers. Tagging @pscholer, @cheidegg. The current (deactivated) file sTGC_Digitization_EffChamber looks very bizzar to me
• Use double instead of float everywhere
• Use the MuonGM::DetectorManager from the conditions store instead of the one of the detector store
• Avoid multiple copies of digits and SDO objects
• Fix bugs in the vmm-hit merging & in the neighbour logic

Asking for explicit approval of @pscholer, @alainb review-pending-expert