add energy weighted linking
started work on new clusterizer
Merged refs/pull/6057/head from repository cms-sw
first working version of new HGC clusterizer for EM clusters
Merged new_hgc_clusters from repository lgray
fix initial bugs in EM clustering
Merged new_hgc_clusters from repository lgray
Merged refs/pull/6148/head from repository cms-sw

Conflicts:
	RecoParticleFlow/PFClusterProducer/src/Basic2DGenericPFlowPositionCalc.cc
add shower axis to PFCluster for HGC
use PCA as 3D shower position calc
Merged new_hgc_clusters from repository lgray
fix issues in PCA calculator
PCA figured out
update interface of InitialClusteringStepBase to allow consumes collectors and event product retrieval
infrastructure for track assisted clustering
get kdtrees ready for track-based search
track assisted clustering builds sensible cluster stubs
add all layers energy calibration
only cluster HGCEE for now
first import