Removed link to old codec page

Removed link "See <<codec-bloom-load>>" for the codec page does not exist anymore.
Test: Improved CLI testing infrastructure

Added a CaptureOutputTerminal class to the infrastructure, which can be used
in tests, to make sure that CLI commands write out the right data
Internal: removed needless serialization code from TransportIndexReplicationAction and corresponding request object

TransportIndexReplicationAction is always executed locally, as an internal action that is part of either delete by query or delete (when routing is required but not specified). Only the corresponding shard level requests get sent over the transport, hence no transport endpoint is needed for the index version, nor the index request itself is supposed to be sent over the transport.

Moved classes from org.elasticsearch.action.delete.index to org.elasticsearch.action.delete and adjusted visibility so that internal requests are not public anymore.

Also removed serialization code from IndexDeleteResponse as it never gets sent over transport either.

Closes #7211
Core: Improve XContentBuilder API.
Internal: refactored TransportSingleCustomOperationAction, subclasses and requests

TransportSingleCustomOperationAction is subclassed by two similar, yet different transport action: TransportAnalyzeAction and TransportGetFieldMappingsAction. Made their difference and similarities more explicit by sharing common code and moving specific code to subclasses:
- moved index field to the parent SingleCustomOperationAction class
- moved the common check blocks code to the parent transport action class
- moved the main transport handler to the TransportAnalyzeAction subclass as it is only used to receive external requests through clients. In the case of the TransportGetFieldMappingsIndexAction instead, the action is internal and executed only locally as part of the user facing TransportGetFieldMappingsAction. The corresponding request gets sent over the transport though as part of the related shard request
- removed the get field mappings index action from the action names mapping as it is not a transport handler anymore. It was before although never used.

Closes #7214
Internal: moved every single index operation to not replace the index within the original request

Moved get, multi_get, explain, analyze, term_vector, multi_term_vector, index, delete, update, bulk to not replace the index name with the concrete one within the request.

Most of those requests hold now a concreteIndex, with package private getter and setter, that will be set by the related transport action and serialized over the network. This way the change cn be applied in a backwards compatible manner.

Note: TransportShardSingleOperationAction#resolveRequest doesn't need to replace the index with the concrete one in any case, removed that line of code and left default empty impl. The only actions that don't override the method are in fact shard level actions which already contain the concrete index and don't even need to call concreteSingleIndex. The actions that need to do it already override the method by adding additional logic (e.g. filtered aliases, routing etc.)

Improved tests by randomly introducing the use of an alias, and verifying that the responses always contain the concrete index name.

Also cleaned up TermVectorRequest javadocs and ExplainActionTests and AnalyzeActionTests