global: enhance unit test for LazyDict

* Add unit test for the class LazyDict.

Signed-off-by: Leonardo Rossi <leonardo.r@cern.ch>
utils: datastructures docs and PEP257 improvements

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>
base: dropdown menu improvement

* Fixes class name for higlight of new messages.

* Adds min-width for admin panel.

Signed-off-by: Adrian Pawel Baran <adrian.pawel.baran@cern.ch>