Monitoring stack, included in webrunner and KVM SR

/reviewed-on !66

otherwise system libdb can be linked.

/reviewed-by @kirr
/reviewed-on !62

@kazuhiko also says:

with our current usage on gitlab, missing RPATH is not an issue but if
you invoke './parts/icu/bin/makeconv', it fails before my change.

/reviewed-by @kirr
/reviewed-on !62

* patch nltk egg so that the default data location is (buildout_directory)/parts/nltk-data without explicitly specifing by NLTK_DATA environment variable.
* download collection can be overridden like 'collection = aaa bbb ccc'.

/ref http://community.slapos.org/forum/NLTK-Buildout--Download-and-install-nltk_data

/cc @klaus, @Kreisel 

/reviewed-on nexedi/slapos!58

To pick up

    nexedi/gitlab-workhorse@32ec77c4

/reviewed-by TrustMe  (I hope)