Disable RestTable headers by default.
Add TimestampedTable subclass.
Add _cat/health.

% curl localhost:9200/_cat/health\?v=1\&ts=0
cluster  status nodeTotal nodeData shards pri relo init unassign
kluster green          1        1     20  20    0    0        0

% curl localhost:9200/_cat/health\?ts=0
kluster green 1 1 20 20 0 0 0

% curl localhost:9200/_cat/health\?v=1
epoch      time     cluster  status nodeTotal nodeData shards pri relo init unassign
1383341092 16:24:52 kluster green          1        1     20  20    0    0        0

% curl localhost:9200/_cat/health
1383341119 16:25:19 kluster green 1 1 20 20 0 0 0

Closes #4050.