db/models:
db/models:

Made SESCollection and SES DB models iterable (enables the SES XML serializer
to just walk down the tree to serialize).


Former-commit-id: 624e638ed000d1d8612c3e106a5768c46e65eb1c [formerly f824c64727ddbbfb87f664e1fa46b3f903752c9e] [formerly f824c64727ddbbfb87f664e1fa46b3f903752c9e [formerly 1a4c6c4faa5a1addfda89a8d50568354ecca5e5f]]
Former-commit-id: b5d6294eef753294082280bdd8dc84c32c20b182
Former-commit-id: 337baf5f49db90c03287fa51b2c62c920c19a248
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine