fieldformatter → expression Relation

File in src/core/fieldformatter	Includes file in src/core/expression
qgsrelationreferencefieldformatter.cpp	qgsexpressioncontextutils.h
qgsvaluerelationfieldformatter.cpp	qgsexpressioncontextutils.h
qgsvaluerelationfieldformatter.cpp	qgsexpressionnodeimpl.h
qgsvaluerelationfieldformatter.h	qgsexpression.h