Nth PR on develop branch for easybuild-docs, for N=6


Hi @boegel, @stdweird,

I think the new structure is better visible at this point; can you validate?
Best way to visualise it is this one: http://easybuild-docs.readthedocs.org/en/develop/
However, giving the feedback in github style over here would help it advance faster, I guess...
Second thoughts: leave this section in here, point to here from `Writing easyconfigs`?

`--list-easyblocks` is a commonly used command line option, but not part of typical workflow