build improvements
- add optional localbuildsettings.py
- remove the 'jonatkins' and 'jonatkins-dev' from buildsettings.py - some devs were using them and it'll give them unexpected update behaviour
- add a 'local' build - uses the public release for external resources (rather than a local web server as for local8000), but no distUrlBase. perfect for code-only changes
- distUrlBase can now be None - no more wacky invalid URLs

(the resourceUrlBase will become redundant once all resources are embedded, but that's still pending)