OPENDJ-832 Leverage the work queue for processing requests received on the HTTP connection handler 

Implemented async search operation.
Added support for canceling tasks.

SdkConnectionAdapter.java: ADDED

CollectClientConnectionsFilter.java:
Hooked the async implementation instead of the synchronous InternalClientConnection.

HTTPClientConnection.java:
Implemented sendResponse(), sendSearchEntry(), sendSearchReference(), disconnect(), getOperationsInProgress(), getOperationInProgress(), removeOperationInProgress(), cancelOperation(), cancelAllOperations(), cancelAllOperationsExcept(), getNumberOfOperations().
Added addOperationInProgress() and isConnectionValid().

procotol*.properties:
Renamed MILD_WARN_LDAP_CLIENT_DISCONNECT_IN_PROGRESS_166 to MILD_WARN_CLIENT_DISCONNECT_IN_PROGRESS_166.
Removed INFO_HTTP_CONNHANDLER_STARTTLS_NOT_SUPPORTED_1515.