Auto remove unwanted deps

long awaited good shit finally arrives to easybuild :)

this is not ready to merge, still needs some more work, like translating shit to every language

this is working now:

```
eb -r --dry-run SAMtools-0.1.19-goolf-1.4.10.eb --shit=zlib,ncurses
```
@pescobar: in my opinion, 'filtering' is a more appropriate term here that 'ignoring', so use `--filter-deps` instead?

Also, maybe you should automagically extend the list of OS dependencies with the things that are being filtered out?

That way, EasyBuild will make sure that all dependencies (it knows about) are available one way or another...

The downside of that is that you need a mapping of software name to OS package name (which is different depending on the OS).