Third-party libraries can now provide their own mojo services. They do
so by adding a config.yaml file to their pub package which contains
- a list of service names and java classes which handles that service's
  registration.
- a list of pre-built .jar files to statically link with the app's shell
  when building the app.

Very simple so far. This schedules an alarm to fire once a day, kicking
off a service that downloads a new app.skyx from a hardcoded URL. The
new skyx replaces the current one.

@abarth

@abarth

@abarth

This is just one of many steps in preparation for turning
fitness into a play-store ready app.

@abarth @collinjackson