INT-3231: Fix Tail setters types for SPR 3.1.x

JIRA: https://jira.springsource.org/browse/INT-3231
INT-3228: Remove Previous versions' Deprecations

JIRA: https://jira.springsource.org/browse/INT-3228

Remove elements that were deprecated in earlier
versions; see the migration guide for more information

https://github.com/spring-projects/spring-integration/wiki/Spring-Integration-2.2-to-3.0-Migration-Guide

INT-3228: Revert FileTransferMH#setTempDirectory
INT-3221: Deprecate MessageTransformingCI

JIRA: https://jira.springsource.org/browse/INT-3221
INT-3220,INT-3224: Fix Twitter & Channel docs

JIRA:
https://jira.springsource.org/browse/INT-3224
https://jira.springsource.org/browse/INT-3220
INT-3221 Polishing

Remove unused import.

JIRA: https://jira.springsource.org/browse/INT-3221
INT-3230 Added support for 'load-balancer-ref' attribute
 of the 'channel' element. Added tests and updated documentation

INT-3230 addressed PR comments