Internal: remove unused constructor and adjust methods visibility in DelegatingActionListener
Java api: remove needless copy constructor from DeleteIndexedScriptRequest
Internal: fix members visibility, remove unused constant and needless try catch in indexed scripts transport actions
Java api: change base class for GetIndexedScriptRequest and improve its javadocs

`GetIndexedScriptRequest` now extends `ActionRequest` instead of `SingleShardOperationRequest`, as the index field that was provided with the previous base class is not needed (hardcoded).

Closes #7553
[TEST] resolved warning in IndexedScriptTests
_boost: Fix "index" setting

Serialization if "index" setting for boost did not work since
the serialization was just true/false instead of valid options
"no"/"not_analyzed"/"analyzed".

closes #7557
[TEST] replaced assert with actual assertions in TemplateQueryTest
[TEST] added test to verify GetIndexedScriptRequest serialization after recent changes
Aggregations: Fixes resize bug in Geo bounds Aggregator

Closes #7556
TransportClient: Mark transport client as such when instantiating

This allows plugins to load/inject specific classes, when the client started
is a transport client (compared to being a node client).
incorporated review comments