Added the class AliFMDGeometryBuilder (and derived

Added the class AliFMDGeometryBuilder (and derived
AliFMDGeometryBuilderSimple) that defines the geometry.  AliFMDGeometry
uses that class.   AliFMDGeometry can also get crucial information from
a predefined class (but more needs to be extracted from the TGeoManager).
The code has been changed to reflect this.  In particular, the class
AliFMDSimulator is largely obsolete.   I've kept it for a while, as I'd
like to test what penalty  one endure from such a class.   I believe
it is negligible, but Federico thinks it's not.

The AliFMDG3Simulator and derived can essentially disappear.

Fixed some compilation warnings in AliFMDReconstructor.