Nth PR on develop branch for easybuild-docs, for N=5

still bits and pieces to improve, but ok to receive the first round of feedback
no tip, flesh out:

Combine `-a` with `--easyblock`/`-e` to include parameters that are specific to a particular easyblock; by default, the ones specific to the generic `ConfigureMake` easyblock are included. For example::

```
$ eb -a -e EB_WRF
```

(no output too long, avoid 'hacks')