Rename Transpose to TransposeTupleToBag

Also removed some log spam, added some javadoc.
Add exec and accumulate tests for Sessionize
Make SessionCount also implement Accumulator interface

Also added exec and accumulate test cases.
Don't expose certain classes in javadocs to make them cleaner
Sampling documentation cleanup
Minor doc fixes [ci skip]
Doc change [ci skip]
Doc change [ci skip]
Merge pull request #51 from matthayes/master

Sessionization improvements