Add missing mappers to MapperBuilders.

 - completion
 - geo_point
 - geo_shape
 - parent
 - size
 - ttl

Close #4423
Add more information to IndexInput failures related to abusing closed input
Also wrap IndexInput if CFS is used
Simplify nodes stats API

First, this breaks backwards compatibility!

* Removed /_cluster/nodes/stats endpoint
* Excpect the stats types not as parameters, but as part of the URL
* Returning all indices stats by default, returning all nodes stats by default
* Supporting groups & types in nodes stats now as well
* Updated documentation & tests accordingly

Closes #4057
Allow to set "level" parameter to "shards" and "indices"

"cluster" does not make a lot of sense in nodes stats

TODO: Squash with the other commit after review