[sugar] Update.1 activities download script

[Mikus Grinbergs]

Tried 'update-activities.py -l' from 700.  It failed in 
/usr/lib/python2.5/urllib.py on "url error  invalid proxy for http"

I do not have wireless.  I do have wired ethernet, which goes 
through a proxy to reach the internet.  I *am* able to issue 
'olpc-update joyride-1769' from the same 700 command line, and have 
it download (and install) 1769.  The same ethernet+proxy connection 
is used; I've specified the proxy through environmental variables.

mikus