- New virtual function in AliMUONVGeometryDESegmentation and in the daughters GetDire...

- New virtual function in AliMUONVGeometryDESegmentation and in the daughters GetDirection().
This returns an enum defined in AliMUONGeometryDirection kDirX, KDirY and kDirUndefined
This method gives the direction where the pad size of the chamber is constant.
In other words this corresponds with the coordinate where the spatial resolution is the best.
Normally kDirY will correspond with cathode segmentation for the bending plane and
kDirX  with cathode segmentation for the non bending plane