[Docs] added document for the lenient option in match queries
[Docs] updated refrences to dynamic_date_formats
Added initial documentation for the redesigned percolator.
[Docs] update reference to remove documentation about percolating during an index, bulk or update request.
Added brief overview of the python client to the guide
Added a link to official Python client to the client list, fixed perl link
Terms facet will now throw a parsing exception if no field, fields or a script is supplied.

Previously you'd get an NPE. Also added extra exception when called with unknown parameters.
Java API Documentation (0.90+) needs update for accessors in Facets docs
Closes #3921.
(cherry picked from commit a753c48)
[DOCS] How to check max_file_descriptors
Settings queue_size on index/bulk TP can cause rejection failures when executed over network
The #3526 fix was not complete, it handled cases of on node execution, but didn't properly handle cases where it was executed over the network, and forcing the execution of the replica operation when done over the wire.

This relates to #3854

closes #3929
Fix teh typos in javadocs
phrase_len is not called phrase_length
Allow awareness attributes to be reset via the API

Currently we don't allow resetting the awareness
attribute via the API since it requires at least one
non-empty string to update the setting. This commit
allows resetting this using an empty string.

Closes #3931