* add a dev/dartdoc.dart script to generate docs for the packages/ packages
* remove description
* rename readme
* change to using --include-external
* move docs to dev/docs
This will work after the next Engine roll. Currently it requires
a fix to tracing which isn't in the released engine.
Next steps are to make this work on a bot, and to add iOS support.
@abarth @chinmaygarde