Add "public-project?" checkbox to new-project view 

My impression is that being public or not is such a important choice, that it should be displayed when creating a 
new project. 
It does not make the new-project page more cluttered because the warning/explaination at the beginning 
of the page can now be removed.

![new-proj](https://f.cloud.github.com/assets/241247/1138269/6af2f3cc-1c72-11e3-8133-1ad8acf2aa39.png)

The default for that checkbox is determined by the global default setting. If this change is in principle acceptable, I will try to write a proper test; Still need to figure out how to do that though.