A xReader is a function that read a mesh file into a mesh database with
eventually a DATAMANAGER created to keep element id association.
This last point use the DATAMANAGER concept (xUnorderedMapDataManager,
xGeneralUnorderedMapDataManager or xAttachedDataManagerAOMD) to
associate to an element of the database its id in the file read.

For now only msh file format reading is proposed with a xMshReader
template functions located in xMeshTool/xReader. It can be easily
completed by other template function to read Abaqus/Nastran/ ...
file format.

It is specialize for AOMD data base and xAttachedDataManagerAOMD (for
DATAMANAGER ) in  xInterface/AOMD/general/src//xMshToAOMDReader.h.
Implementation is largely inspired from AOMD_Util::importDGFile.
It support msh version 1 and above 2 format.
It can be used in place of AOMD_Util::import call in eXlibris.
Note that only elements, file format and nodes block are read. Other
blocks are ignored ....