Fix schemagen_core paths + merge CXxx and CXxxImpl into classes/

- schemagen_core: output path simplified to ../../src/schema/entity (no
  longer self-referential via /home/), enums removed (handled by schemagen)
- CXxx classes regenerated into src/schema/entity/classes/ (717 files)
- CXxxImpl classes moved from iclasses/ to classes/ alongside CXxx (642 files)