Add methods to get info about sTGC single wire

Information about sTGC single wire is available in geometry, so should be accessible. In particular during digitization, evaluating time of arrival of a hit, i.e. the time between ionization and signal formation, requires the wire position. So accessor methods are added to get the sTGC wire pitch, wire number, number of wires and position of the 1st wire. Wire position can be calculated using these parameters.