Fixed an ordering problem in risk disaggregation
Changed a couple of event based tests due to the change in the ordering
Fixed the export test
Merge pull request #1493 from gem/filtering-sources

Ordering the sources after filtering-splitting
Merge pull request #1491 from gem/fix-risk-disagg

Fix risk disaggregation
Merge branch 'master' of github.com:gem/oq-engine into db-migrations
PEP8 fixes