[Docs]  Add experimental highlighter plugin
[DOCS] Added tables and fixes to upgrade.asciidoc, fixed version in README.textile
Author: Sean Gallagher
Date: 10 Apr 2014 15:23 EDT
Fixed an where a nested `nested` aggregation falls outside of its parent `nested` aggregation bounds.

The nested `nested` aggs now gets the proper parent docs that define its bounds correctly.

Closes #5728
The clear scroll apis now optionally accepts a scroll_id in it body.

Closes #5726
Ignored clear scroll rest test
[TEST] Prevent TTLPurger from recreating deleted index

Related to #5766
Each search request should use a new InternalSearchResponse instance even in case when all shards return no hits.
The InternalSearchResponse may get modified afterwards, so a new instance required at all times.
Strengthening pseudo random number generator and adding tests to verify its behavior.

Closes #5454 and #5578
Added a AppendingDeltaPackedLongBuffer-based storage format to single value field data

The AppendingDeltaPackedLongBuffer uses delta compression in paged fashion. For data which is roughly monotonic this results in reduced memory signature.

By default we use the storage format expected to use the least memory. You can force a choice using a new field data setting `memory_storage_hint` which can be set to `ORDINALS`, `PACKED` or `PAGED`

Closes #5706
lightweight minimum master node recovery
don't perform full recovery when minimum master nodes are not met, keep the state around and use it once elected as master
make no master lock an instance var so it can be configured