base: bundles block

* Adds a block to overwrite the base bundles set.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
base: bundles structure changes

* Makes bundles follow the rule: base shared bundles are separated
  from modules bundles.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>