Drop Defrac prefix if unnecessary

- If a class is a Util, it should start with Defrac in order to avoid
  confusion
- If a class is a type (like DefracFacetType) it should start with
  the Defrac prefix
- If a class belongs to a type (DefracSdkAdditionalData belongs to
  DefracSdkType) the prefix should be kept as well
- If none of the previous rules applies, the prefix should be dropped