Updates to use docools version 12
REST transactions: documentation and timeout improvements.

o Re-write most of the English in the documentation.
o Add note about using REST transactions in HA.
o Replace StatusCode annotations with constructor parameters.
o Avoid race conditions when rolling back timed out transactions.
REST transactions: minor cleanup.

o Advertise transaction endpoint among database hyperlinks.
o Enable logging for cypher ExecutionEngine.
o Use more general types where possible.
Update CHANGES.txt for 2.0.0-M02
Code cleanup

o Cleaned up high prio findbugs warnings.
o Removed unneccessary modifiers from fields and interfaces, reported by PMD.
Merge remote-tracking branch 'origin/2.0' into peg
Introduce Path vs PathPattern
Add shortestPath