layertree → vector Relation

File in src/core/layertree	Includes file in src/core/vector
qgslayertree.cpp	qgsvectorlayer.h
qgslayertreemodel.cpp	qgsvectorlayer.h
qgslayertreemodellegendnode.cpp	qgsvectorlayer.h
qgslayertreeutils.cpp	qgsvectorlayer.h