Fixing up examples for 5.0 & Live DDL

1 commit per app (I'm getting better at this).
Remove VoltCache.
Update lots of readme files to use markdown and to push for liveddl.

I think these could use another pass before 5.0 to try to simplify further, but this should be a step in the right direction.
plannertester has a config with a dependency on the voltcache ddl.  You can either remove the voltcache plan tests (they are pretty simple and likely redundant) - or put the ddl somewhere that plannertester can find it.  See tests/scripts/plannertester/voltcache/config