UP-4223:  Enhance ChainingProfileMapperImpl to provide a stickySelection...

... feature

https://issues.jasig.org/browse/UP-4223

Add support for a stickySelection feature: if enabled (it's off by default), a user's choice of a specific profile will be remembered until s/he makes another specific choice. In other words, choosing a non-default profile makes it your own, personal default from there forward.
:cool: . Love the move to `ToStringBuilder`.