Merging in changes from lp:~amcg-stokes/fluidity/multimaterial_diagnostic_dependencies. This changes the behaviour of diagnostic algorithm's dependency search when material_phase support is set to multiple. It now searches across all material_phases for FieldName. The behaviour when material_phase_support is set to single or when StateName::FieldName is given is unchanged. This has been tested using the example of bulk_viscosity under Viscosity which now depends on MaterialViscosity (requires options file that use it to be updated), which is found across all material_phases as it should be.