Distributions page update

[Joachim Steiger]

hi, thanks for reworking and extending it.
after explaining the same thing multiple times the last few days, i've
added some more details and explanations where i saw fit.
i am a very bad documentation-writer i fear, i can explain stuff, but i
need the feedback of the confused face to know how much detail to add. ;)

so feel free to refine and reword, and do not worry to ask if something
needs more explaining.

regards

-- 

Joachim Steiger
Openmoko Central Services