Implemented a MemoryMonitor to debug memory consumption issues
Removed sa_period and sa_damping from gmf_scenario
Merge branch 'master' of github.com:gem/oq-engine into performance-monitor
Enhanced the PerformanceMonitor and relative tests
Added forgotten file
Removed gmf_scenario.result_grp_ordinal
Implemented a new distribution per block of sites in the scenario hazard calculator
Cosmetic change
Merged from master
Merged from master
Fixed the qa tests for scenario_risk
Added python-psutil dependency
Merged from master
bin/oq_create_db:

Get the proper oq-engine version from the python package.
db/schema/load.sql:

The static revision info has been moved to the oq_create_db script. It also no
longer uses hard-coded version numbers.
improved docs
performance:

Recover gracefully if psutil can't read process memory info due to an
AccessDenied error. If this happens, the process in question is discarded
from the monitored and is not checked anymore.
Various fixes according to Luigi suggestions
Small improvements to the PerformanceMonitor
Merge pull request #1065 from larsbutler/correct-version-in-db-script

Correct OQ engine version in db script

[r=micheles] [f=*trivial]