fix hazard export
fix hg when some rupture does not produce shaking
updated qa (regression) tests with new data and fixed the seed generation
use more meaningful iteration variable name
Merge branch 'master' of https://github.com/gem/oq-engine into aal-loss-curves
added average loss computation
first implementation
improved variable naming and docs
improved docs
Merge branch 'master' of https://github.com/gem/oq-engine into fix-1149270
Updated tests, updated ref to get_gmfs_per_site
added a proper test for sd-imt
tests/export/hazard_test:

Fixed a broken scenario hazard export test.
qa_tests/_utils:

Added base QA test class method for testing with variable precision.
qa_tests/hazard/event_based/case_2:

Added event based QA test, case 2.
qa_tests/hazard/event_based/case_4:

Adapted case 4 for the event-based calculator.
qa_tests/hazard/event_based/case_8:

Initial draft of case_8 for the event-based calculator.
qa_tests/hazard/event_based:

Fixed imports.
tests/export/hazard_test:

Removed a false comment.
Merge pull request #1081 from larsbutler/scenario-export-fix

Fix a broken scenario hazard export test

[r=micheles] [f=*trivial]