ENG-4367 changes, cleanup

- removed instructions to open a terminal window and run the "launch
voter" script, replaced with instructions to open two terminal windows
and run "./run.sh" and ".run.sh client".
- same for voltkv
- updated links to documentation on voltdb.com
- removed "Getting Started" tab which didn't render correctly
- Made "Next Steps" the last page.
- removed "Cool Tools" tab.  Added instructions for using VoltDB Studio
and SQLCMD within the Voter and VoltKV instructions.  Having this as
the last page is awkward.
Add Joiner interface which extends RejoinCoordinator.
Add new start action "join". Currently very simple, will be polished to support
different joins later.
Modify start up sequence to allow node joining the cluster with new partitions.
Move ownership of TaskLog from Site to JoinProducer.

Extracted a base class from RejoinProducer that could be used for JoinProducer
later.
Add JoinProducer which extends the JoinProducerBase to the initiator.
Rename startRejoin() in RejoinCoordinator to startJoin() and returns a boolean
to indicate success.
Refactored RealVoltDB's initialization code to initialize join coordinator and
generates correct topology to construct other components.
Initialize the hashinator using the partition count in RealVoltDB instead of
calculating from the deployment file.
Make LeaderAppointer watch the parent initiator ZK node for added partitions.
Merge remote-tracking branch 'refs/remotes/origin/elastic' into wip-4246

Resolved conflicts:
	src/frontend/org/voltdb/Inits.java
	src/frontend/org/voltdb/RealVoltDB.java
	src/frontend/org/voltdb/iv2/Cartographer.java
For ENG-4396, do the same murmur3 long hashing cleanup in the EE.
Merge pull request #389 from VoltDB/ENG-3838-json-array

ENG-3838 JSON ARRAY_ELEMENT, ARRAY_LENGTH
Merge pull request #396 from VoltDB/ENG-4345-aggexec

Eng 4345 aggexec
ENG-4290 Multi-COW fix checkpoint.
Deleted content that was already commented out
Fix casting errors pointed out by Ning
ENG-4290 Rename COWStream... to TupleOutputStream...
Merge pull request #402 from VoltDB/ENG-4367

ENG-4367 Demo Dashboard instructions
Integrate with Ariel's hashinator changes. Update the hashinator config in
UpdateTopology.