Add static property for default RedisConnection port

Motivation:

The default port for Redis is well published to be 6379, and it is common to want to pass this value around or use it as a static default value in methods and initializers.

Modifications:

Add RedisConnection.defaultPort static property for all users to use, and update references of the 6379 literals to use new the new property.

Result:

Users should have a reliable default defined to use everywhere to avoid bugs.