So far, we need to bypass application object for modules to emit
a event.  This make EventManager portable and easy to pass event
emitter.  This brings modules less coupled with application object.

This allows builders to emit a final epilog message containing
information such as where resulting files can be found. This is only
emitted if the build was successful.

This allows us to remove this content from the 'make_mode' tool and
the legacy 'Makefile' and 'make.bat' templates. There's room for more
dramatic simplification of the former, but this will come later.

Signed-off-by: Stephen Finucane <stephen@that.guru>

- use the entry point to load the extension module in the usual way
- update the documentation to reflect this change