Recipes for setuptools, zope.interface and twisted

[str4d]

Closes #454.

The build will fail until #450 is closed, but you can manually fix the filepath:

$ cd ~/.local/share/python-for-android/build/other_builds/twisted/armeabi
$ mv twisted Twisted-15.4.0/bin/_preamble.py
$ mv Twisted-15.4.0/ twisted

and then run the build again.

[inclement]

I've added these recipes manually in a slightly different way, abstracting away the way hostpython is called to a new attribute of the PythonRecipe (though it has a terrible name that I will change), and an option to install in the hostpython build dir. This should hopefully make it easier to do the same thing with other recipes.

I didn't include your commit because of big merge conflicts thanks to my big rebase to get the revamp into the master branch, but I think I've realised how to do so and will cherry-pick it manually to keep it in the history. I'll leave this PR open until then.

Are you able to test if I got it right, and the new twisted etc recipes work? I checked that they build but don't have examples to test with. The problem with folder unpacking may also be solved thanks to another commit.

Thanks!