first pass
merge commit
updated the schema
fix exposure for qa tests
fixed insured losses computation
updated unit test as the renaming
Merge branch 'master' of https://github.com/gem/oq-engine into scenario-insured
Merge pull request #1061 from larsbutler/silent-db-script

DB schema bootstrap script now runs silently by default

[r=matley] [f=*trivial]
Merge pull request #1060 from larsbutler/fix-agg-loss-export-test

Fix aggregate loss export test

[r=matley] [f=*trivial]
Merge pull request #1062 from larsbutler/fix-cls-haz-qa-case-11

Stabilize classical hazard QA test case 11

[r=matley] [f=*trivial]
Merge pull request #1053 from matley/scenario-insured

Scenario insured losses
db/fields:

Added NullFloatField type.
tests/db/fields_test:

Added tests for NullFloatField.
db/models:

`truncation_level` is optional, so I changed the model field type to
NullFloatField.
db/models:

WIP for fetching GMFs by location.
qa_tests/hazard/event_based/spatial_correlation:

WIP for spatial correl. QA tests.
db/models:

Added functionality to filter GMFs by location when iterating over the GMFs in
a GmfSet.
db/models_test:

Added a test for when `iter_gmfs` is called with a `location` specified.
qa_tests/hazard/e.b./spatial_correlation/_utils:

Added util functions for computing joint probability and getting all ground
motion values for a given location and job.
qa_tests/hazard/e.b./s.c./case_1/job.ini

Corrected random_seed to match the random seed in the example test script
included with the bug description.