[Sugar-devel] Can we be a little more friendly to Ubuntu users

[Ma Xiaojun]

I made some change to
http://wiki.sugarlabs.org/go/Sugar_Creation_Kit/sck/Advanced_Topics#Sweets_Distribution
This section is linked from the Ubuntu page.

I think it is slightly more clear now.
I do not why the section title was used for the maybe most important
link. This confused me at least.
The raw repository link (rather than apt line) was not so friendly. So
I replaced it with the Sweets_Distribution wiki page. People can find
real instructions here, at least.
Also, because instructions for synaptic is not available yet. I
changed "synaptic" to more general "apt".