[sugar] Running from the source directory

[Marco Pesenti Gritti]

Hello,

it's now possible to run sugar from the source directory. Something like
this should work:

./sugar-jhbuild shell
cd source/sugar
./sugar-emulator

The only thing which is still running from the installation directory
are the services scripts. It should not be a big problem in practice
because they are loading the actual code from the source directory too.

If you find any bugs with this please let me know.

Marco