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.
I guess I choose those words less than perfectly.  In the process of implementing, I had occasion to look into what this method really did.  Having learned it, I thought I'd document it.  By "mutable copy" I really mean "you have the same copy as the IPerson instance itself -- your changes will apply to the original object."

And t's not what I usually consider a good idea.  I prefer state-changing things to happen via an API that looks like the owning class has an opportunity to react/reject, even if currently it does no such thing.