Enable the use of sTGC as-built conditions

Since sTGC as-built condition parameters are almost ready, let's enable the instantiation of the respective tool for validation tests. So, the activation of NSW (both MM and sTGC) as-built conditions is now possible via job options. We still need them to be included in a global conditions tag before enabling them by default. For convenience, a flag is added into MuonDetectorCondAlg so that we may turn off either MM or sTGC as-built independently.

Tagging also: @stsigari