Rename database columns:
* disease_occurrence.system_weighting -> machine_weighting
* admin_unit_disease_extent_class.has_changed -> has_class_changed
Fixes to previous commit
Fixes following review
Merge branch 'master' into 178-189-database-and-hibernate-columns

Conflicts:
	src/DataAcquisition/src/uk/ac/ox/zoo/seeg/abraid/mp/dataacquisition/weightings/WeightingsCalculator.java
Merge pull request #117 from SEEG-Oxford/178-189-database-and-hibernate-columns

Rename database columns