Cleanup to the SDG dependency repository references, preferring Spring IO Repos over external repos (such as dist.gemstone.com). Added conditional logic around the GemFire 8 Distribution Configuration Properties in the CacheFactoryBean in an effort to enable SDG 1.5 to work with GemFire 7.x versions and earlier.  Refactored the GemfireUtils class's logic for detecting GemFire Versions at runtime.