software/kvm: Drop development profile

It's never used, and that's not the repetetive nor deploy-like way of doing
development in the end.

software/kvm/development.cfg

-# Development profile of kvm.
-# Exactly the same as software.cfg, but fetch the slapos.cookbook and
-# slapos.toolbox from git repository instead of fetching stable version,
-# allowing to play with bleeding edge environment.
-
-[buildout]
-extends = software.cfg
-  ../../stack/slapos-dev.cfg
-
-parts +=
-# Development eggs
-  ${:common-parts}