registry of transport handlers

LegacyPackageHandler register for 'unknown' transport type
Merge branch 'package-loader-etc' into requirejs-wip
fix parser generation; correct AMD header
boot.js dependencies simplified
boot, smalltalk, nil, _st have explicit IDs
amberc now loads and runs with requirejs

output still does not run, define missing
hacked amberc so it now compiles and runs tests
Formatting
Merge pull request #557 from herby/requirejs-wip

amberc now produces runnable files from AMD modules; tests are run