audit rule update/delete
Updates can now be emitted from RulesImporter (uploaded manifests).  Events now stored in the database (fixed bug with non-nullable fields set null)
fixed whitespace style, removed unused import
events sent after updates rather than before
changed empty string to null in event factory.  More consistent now
rules delete event created after deletion, rather than before
Merge pull request #205 from candlepin/ckozak/rules_audit

ckozak: rules audit