FeatureEnvy: Fix handling of dynamic properties.

There's no Ivar in this case.  So instead, just consider the setter and
getter methods and the interface that contains them.
Fix brace style
Fix FeatureEnvy handling of class methods

Use getReceiverKind to determine if the receiver is an instance or class.
Refeactor FeatureEnvy VisitObjCPropertyRefExpr

Split member function up into smaller functions.