Change IDToTermCache ivar from an NSCache to a NSMapTable.
Removed unused, commented out code.
Added NSData gtw_trucatedCompare: method.
Added GTWAOFBTreeNode enumerateKeysAndObjectsInRange:usingBlock: method.
Changed GTWAOF into an immutable protocol and created a new GTWMutableAOF protocol.
Added new GTWAOFBTree rangeOfKeys:matchingPrefix: method.