Rich : Use MsgCounter instances for warnings and errors

Rich : Migrate away from GaudiAlg Error(...) and Warning(...) base class methods to MsgCounter instances.

In some situations where message suppression is not really needed (e.g. during initialize() where an error code is anyway going to be returned) just use basic xyz() << stream instead.

@cattanem As messages might change in a few places (as it wasn't always possible to precisely replicate the exact message as before) some diffs might be expected here and also in the Lbcom and Rec MRs that will follow soon.