Add TransactionGraphHelper.

Supplies abstraction for transaction retry strategies.
Refactored the transaction retry helper.
Refactor naming of TransactionRetryHelper methods.
Add test for Exception checks in retries.
bumped to Neo4j 1.9.4.
Fixed problem with embedded maps in lists for GraphSON serialization.
Update changelog.
Merge remote-tracking branch 'origin/master'

Conflicts:
	CHANGELOG.textile
Fixed bug on creating manual indexes