Inequality, Rebalancing, Switches

Added the != operator to queries, debugged the rebalancing function in AVLTree
source, cleaned up conditionals in Query to use switch statements in place of
successive if-blocks.
Bugfixes, Query Printing

Debugged issues with enums in switch statements, added toString methods for
Attributes, successful query should return query statement and then query
matches; restored working version of type-check in Constraint generator.