Switch to new MCStatTools version

This version contains all patches in v4r7* series as well as few developments aimed at making usage more comfortable. Support for XRootD downloading of XMLs is also removed. Basically the XMLs are downloaded only using the LHCbDIRAC Python interface. Further details will/need to be provided on Twiki/GIT README.md. The aim is to tag this version as v5r0 when tests are finished and a code review is done.