Move FunctionBuilder set up code into initializer
Make set_up_argument_relations an instance method
Unify set_up_argument_relations methods
Inline FunctionBuilder#filled_out_template
Limit public interface of method builders
Extract method FunctionBuilder#qualified_method_name
Unify method lines buildup
Collect return value names in ArgumentBuilderCollection
Collect method arguments from argument builder collection
Move method #pre to #pre_conversion
Fix test description
Let ArgumentBuilderCollection collect pre_conversion
Rename methods #callarg to #call_argument_name
Let ArgumentBuilderCollection collect call argument names
Rename #post to #post_conversion
Limit public interface for ArgumentBuilderCollection
Let ArgumentBuilderCollection collect post_conversion
Eliminate NullArgumentBuilder
Partially refactor FunctionBuilder [merges 'refactor-function-builder']