[sugar] sugar-update: your friendly neighborhood auto-installation script

[Eben Eliason]

A new version is available on the wiki.  Here is a summary of changes:

- Changed -o overwrite to -c clean, having the same behavior
- Replaced -v verbose with -q quiet, so progress output is on by default
- Implemented progress updates for downloads

I also reorganized some of the code, so please let me know if you
encounter any problems.

- Eben