Mappers: Better validation of mapping JSON

Closes #7205
[DOCS] Corrected syntax error in search curl cmd

Closes #8447
[DOCS] Expand logging documentation

Updated log4j link so it doesn't point to log4j 2.0 but version 1.2. Clarified which formats are supported and briefly explained what loggers and appenders are, plus added a link to the log4j docs.

Closes #5305
Closes #8455
Logging: Add log4j-extras dependency

Close #7927
[DOCS] Added documentation for log4j-extras dependency
Docs: Changed breaking docs in master to correspond with 1.x for easier merging
Indices API: Fix GET index API always running all features

Previous to this change all features (_alias,_mapping,_settings,_warmer) are run regardless of which features are actually requested. This change fixes the request object to resolve this bug
Docs: Fixed a bad ref to docs-bulk-udp which no longer exists in master
Added quotes to allow spaces in installation path
Removed bwc for GetIndexRequest serialisation
Tests: Improve netty test behaviour

Based on some test failures, this commit fixes two minor things

* Bind ports only on so called ephemeral ports to prevent try to
  bind to ports where elasticsearch already runs on
* Remove @Network annotation as it was used in a wrong scope