new database setting `DEFAULT_MODEL_STORE`, specifying default table storage for models (row vs column)
catch HANA-native integrity error exceptions and reraise them as `utils.IntegrityError`
quote identifiers in queries
added missing imports
Merge branch 'master' into feature/quote_identifier
Merge branch 'master' into feature/integrity_error
Merge branch 'master' into feature/model_store
Merge branch 'feature/model_store'
Merge branch 'feature/quote_identifier'