Convenience method for accessing annotation that may be associated
either directly on property, or, if not, via enclosing class (context).
This allows adding baseline contextual annotations, for example, by adding
an annotation for a given class and making that apply to all properties
unless overridden by per-property annotations.
This method is functionally equivalent to:
MyAnnotation ann = propWriter.getAnnotation(MyAnnotation.class);
if (ann == null) {
ann = propWriter.getContextAnnotation(MyAnnotation.class);
}
that is, tries to find a property annotation first, but if one is not
found, tries to find context-annotation (from enclosing class) of
same type.