[sugar] moving the activity registry into the shell module

[Tomeu Vizoso]

Hi all,

as part of the API cleanup and memory usage reduction efforts, I have
started to look into removing the activity registry from
sugar-toolkit.

Although no other process than the shell should have access to the
activity registry nor be able to start activities, we have some code
in sugar-toolkit that directly uses the registry:

DSObject.get_activities
DSObject.resume

ActivityBundle.is_installed
ActivityBundle.install
ActivityBundle.uninstall
ActivityBundle.upgrade

ActivityCreationHandler._create_activity

So I'm going to start moving this functionality into the shell, and
when nothing remain in sugar-toolkit that depends on the registry,
will remove the activity registry from the API. Hope patches will be
reviewable in this way.

Please comment if you see any problem with this.

Regards,

Tomeu