Refine JedisConnectionFactory.

Introduces private (static) methods (and/or local variables) to simplify and remove duplicate logic while simultaneously removing broken line breaks affecting readability and understanding along with cleaning up some compiler warnings.

Simplifies assertions by making consistent use of Spring Frameworks Assert facility rather than unnecessary conditional blocks.

Refers to state variables using getter (rather than direct variable reference) where applicable helping to improve extensibility.

Deprecates createTopologyProvider(..) in favor of createClusterTopologyProvider(..) for consistent and clarified naming.

Closes spring-projects#2745

Author: jxblum