Prototype implementation plus tiny benchmark
Document and tweak
Documentation tweaks
Defined ReadOnlyExchange
Fix up documentation. Split out separate TraverseVisitorTest
Add missing license header
Remove the hasXXX calls from ReadOnlyExchange per review comment by Nathan
Source code cleanp
Remove ReadOnlyExchange#isValueDefined
Fix Math.min/max
Fix LTEQ, GTEQ and EQ cases
merge pbeaman: Adds new Exchange#traverse methods and a new interface Exchange.TraverseVisitor.

https://code.launchpad.net/~pbeaman/akiban-persistit/tree-visitor-prototype/+merge/140559