Installer should create the datashim namespace

[christian-pinto]

The default installer should create the datashim instead of dlf.

[mgazz]

From a source code point of view we need to :

1. change the default namespace in generated manifests from dlf to datashim
2. change the default namespace in the helm chart from dlf to datashim

We also need to test the following scenario:

1. deployment of datashim from scratch
2. helm upgrade of existing release. In this case the operator should be deployed in the datashim namespace without affecting our ability to access existing datasets