SGF-283 - Updated changelog.
SGF-283 - Prepare 1.4.0.RC1.

Upgraded to Spring Data Commons 1.8.0.RC. Switched to milestone repository.
SGF-283 - Release version 1.4.0.RC1.
SGF-283 - Prepare next development iteration.
SGF-283 - After release cleanups.
Implements SGF-274 removing the use of temporary callback objects passed to the 'templated' execute method for each operation implementation in order to reduce the memory footprint, especially in the context of Repositories.
Re-organized SDG dependency version properties in gradle.properties.
Fixed failing testLookupQueryService test when mocks are not enabled.  In addition, assured the tests passes with or without mocks enabled.
Modified the testLookupQueryService method to use pure mock objects to test the lookup behavior and conditional statements.  Added an assertion to the testLookupLocalQueryService test case to verify that the RegionService.getQueryService() method is 'never' called.
Completed SGF-272 refactoring SDG API Javadoc comments as well as cleaning up all Javadoc warnings reported by the SDG Gradle-based build when building on Java 7 and Java 8.
Add the Spring IO plugin

Configure the Spring IO plugin such that it's only applied when the
build is run with -PplatformVersion=<version>. This platformVersion
property is used to determine the version of the Platform that will
be used when running the springIoCheck task. The plugin can be used
by running a build as follows:

./gradlew clean springIoCheck -PplatformVersion=1.0.0.BUILD-SNAPSHOT -PJDK7_HOME=… -PJDK8_HOME=…

This will test the project on JDK7 and JDK 8 using the dependencies
defined in the latest snapshot of Spring IO Platform 1.0.0.
Refactored and performed cleanup in the Spring Data GemFire Reference Guide.  Added chapter on Bootstrapping a Spring ApplicationContext from GemFire using Gfsh.
Additional Spring Data GemFire Reference Guide changes and additions to round out the new feature documentation in Spring Data GemFire 1.4.