Improvements to devfile v2 factory flow support

[sleshchenko]

Is your enhancement related to a problem? Please describe.

eclipse-che/che-dashboard#175 partially implements factory flow, but some places should be improved, reworked:

1. Namespace should be created if it does not exist.
2. Specify the routing class che.
3. Default editors and plugins should be propagated to the DevWorkspace CR namespace, we should not rely on the DevWorkspaceTemplate registry, like we have after PR

    - name: theia-next
      plugin:
        kubernetes:
          name: theia-next
          namespace: devworkspace-plugins
    - name: machine-exec
      plugin:
        kubernetes:
          name: machine-exec
          namespace: devworkspace-plugins

[l0rd]

I am removing this issue from milestone 1 as we only tracking epics in that milestone.

[sleshchenko]

is implemented in eclipse-che/che-dashboard#175