validate_site_model bug fix, enabling a previously disabled qa test
updated test_validate_site_model to consider a degenerate case
Merge branch 'master' of https://github.com/gem/oq-engine into site_model_validation_bug_fix
removed old comment and unused import
Refactoring, rename of a constant, added a comment
Relaxed constraint db side, kept and update validation rule in validation.py
Added comment to clarify site model convex hull area expansion
replaced because with if :)
Merge pull request #1009 from gvallarelli/site_model_validation_bug_fix

Site model validation bug fix
Updated error message, now it's more helpful to the end user
Merge pull request #1010 from gvallarelli/relax_constraint_truncation_level

Relaxed constraint truncation level.
Merge branch 'master' of https://github.com/gem/oq-engine into scenario_hazard_correlation_model