[sugar] Build changes

[Marco Pesenti Gritti]

Hello,

A lot of exciting changes are going in the Sugar tree. Mainly

* We landed the new Presence Service.
* We are heavily refactoring the Graphics API and controls.
* We started to integrate the new Data Store.

Also, not as exciting:

* We are switching back to Python 2.4 in sugar-jhbuild. (It's unclear if
final will actually use 2.5 as initially planned and it's really bad to
keep developing on 2.5 in sugar-jhbuild and build images with 2.4).

As a result we have a lot of new dependencies. Yesterday I spent some
time to rationalize the jhbuild modules structure. 

I dropped the build-base phase because it was getting too complicated to
maintain. jhbuild has commands to rebuild single or part of the modules
anyway.

If you are brave enough go ahead, do a clean rebuild and let us know
about the problems. Most of the activities will not work because of the
API changes, that's known.

Marco