Improved input handling
Refactored interface EntityRegistry to HasEntityRegistry
Look-up of Items and Itemsets by identifier
Support for 'antecedent', 'consequent' and 'rule' rule feature types
Refactored interface HasAssociationRules to HasRuleValues
Refactored method (and interface) HasReasonCode#getReasonCode(int) to HasReasonCodes#getReasonCodes()
Unified the contract for 'reasonCode' and 'ruleValue' result features (ie. returning null when the rank attribute specifies an invalid value)
Marker interface for result features
Replaced occurrences of StringBuffer with StringBuilder
Employed Guava's preconditions