migrated MdtCalibrationTool to use mag field from cache : ATLASRECTS-5452
migrated MdtCalibrationTool to use mag field from cache, and added support to checkMetaSG to dump out field info in pool file Part of magField client migration https://its.cern.ch/jira/browse/ATLASRECTS-5439 Adding in @christos
Edited by Christos Anastopoulos