Updates to redis repositories

* Ensure prefix ends with period
* Allow prefix and key index to be set separately
Fix type mentioned in javadocs
Don't mask original exception in SpringApplication.handleError

If any @Import (or @Enable*, especially @EnableScheduling) has registered
bean *names* as ApplicationListeners, and the application context wasn't
refreshed fully when it failed, then the listener lookup could fail and
mask the original exception

Fixes gh-253