Grouped the parameters that can be defined for a specific site using the new 'site model'
Grouped the parameters that can be defined for a specific site using the new 'site model'


Former-commit-id: 27046fdc274e0d6a7ae7ee8c135e7143f70dd9d8
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine