Fix: oq-hazard without SLT decomposition

[chrisdicaprio]

To properly support running a full SRM logic tree without decomposition we need at least one of the following

• Flatten the entire logic tree. This is less effiicent** in OpenQuake and would require FlattenedLogicTree --> NRML (Feature: NrmlDocument from FlattenedLogicTree nzshm-model#23)

• PARKED Use extended model (advanced oq NRML inputs) but enforce correlation. This will require that the correlated branches are assembled into single component branches with all sources. This not possible in nzshm-model <0.5 where we can only have 2 sources per branch. Feature: extendedModel nzshm-model#24