Project idea link on the wiki

[Richard Braun]

Hello,

The current path to reach the project ideas page on the wiki is through
the Contributing page, and then the project ideas link inside the first
block. I think we should improve that and do something similar to what
is done for the open issues : create a link in the side menu, right next
to open issues. I believe it's even more important now that the GSoC is
about to start.

-- 
Richard Braun