Adding stgc pads
STGC pads were missing in the RDO->PRD converters, adding them. Not building pad clusters for now: we'll check with the detector group of possible ways to remove cross talk effects. Adding @pscholer and @kluit JIRA ticket: https://its.cern.ch/jira/browse/ATLASRECTS-5551
Edited by Stefano Rosati