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.
Deleted content that was already commented out
Merge pull request #402 from VoltDB/ENG-4367

ENG-4367 Demo Dashboard instructions