Added astropy_healpix

Downgraded numpy to 1.16.2

The pipeline was crashing due a numpy error that is fixed in version >1.16.
meqtrees_cattery was not happy with numpy > 1.16 due his specification:
pkg_resources.ContextualVersionConflict: (numpy 1.16.6), Requirement.parse('numpy<=1.16'), set(['meqtrees-cattery']))
Edited Dockerfile to change the version on the METADATA

Added missing emcee

- Added Lofar Beam to base image
- changed killMS version to the private one
- Added bootstrap cats from https://www.ict.inaf.it/gitlab/lofarit/container-data.git
- ddf container now run as root

Decoupled base and prefactor code into two separate containers and moved to new container names nomenclature.