[DOCS] add azure and gce discovery plugins

Clean EC2 disco doc
Add Azure disco doc
Add Google Compute Engine doc
Fix Zen doc (add `enabled` in `multicast` parameters list) - Fix #5032.
Ignore case when parsing `script_values_sorted|unique` in aggregations.

Close #5009
[DOCS] Removed the experimental label from Tribe, Hot Threads
and Completion Suggester
[DOCS] Updated migration docs for multi_field to point to copy_to
[Docs] value_count supports script per 1.1
[DOCS] Fix terms agg value script example
[DOCS] Make apt/yum repos more visible
Added `cross_fields` mode to multi_match query

`cross_fields` attemps to treat fields with the same analysis
configuration as a single field and uses maximum score promotion or
combination of the scores based depending on the `use_dis_max` setting.
By default scores are combined. `cross_fields` can also search across
fields of hetrogenous types for instance if numbers can be part of
the query it makes sense to search also on numeric fields if an analyzer
is provided in the reqeust.

Relates to #2959
Updated nodes info endpoint in elasticsearch.yml

Relates to #4055
Fixed the string() code literal in the java client index api doc.
[DOCS] organize a bit the repository plugins

(cherry picked from commit 88e1c20c4581885db7e5e65edf7eb3629c2d31ca)
Add fuzzy/slop support to `simple_query_string`

Ports the change from https://issues.apache.org/jira/browse/LUCENE-5410
Add Marvel and Paramedic to config file
add redis transport plugin
[DOCS] Added backwards compatibility instructions to Perl client
Add IndexReader reference counting methods to forbidden APIs.
Be paranoid about double release.
Use patched version of ReferenceManager to prevent infinite loop in
RefrenceManager#accquire()

See LUCENE-5436
[DOCS] delete by query requires a top-level query parameter

Closes #5044
(cherry picked from commit 1e265b3)
Fix BytesRef owning issue in string terms aggregations.

The byte[] array that was used to store the term was owned by the BytesRefHash
which is used to compute counts. However, the BytesRefHash is released at some
point and its content may be recycled.

MockPageCacheRecycler has been improved to expose this issue (putting random
content into the arrays upon release).

Number of documents/terms have been increased in RandomTests to make sure page
recycling occurs.

Close #5021