Missing include (header) files in emcClustering

When running runMC.C on hydra.jinr.ru, error message appears stating that emcClustering/clustering/ClusterElement.h file cannot be found. This comes from the fact, that during the build, file ClusterElement.h is in the second-level subfolder while headers are stored inside include directory without any directory structure (directly in the root of the include folder). The error is visible only in the case, if mpdroot was built on one computer and transferred to another. If run on the same machine, error doesn't occur since library contains full paths of the source files.

In both ROOT and FairRoot, includes are stored in the include directory without additional structure and we will follow this approach. To do so, we will adopt one directory-one library approach. For now 4 new libraries will be created to cope with the emc problem - EmcClustering, EmcKI, EmcHitMaker, MpdClustering. All 4 libraries will be linked to the "base" library Emc.