add hook to ensure unique case insensitive names for groups or stems

Enabled one or both of these hooks to have case insensitive unique names in grouper (e.g. if provisioning to a system which requires that)

set that with grouper.properties:

hooks.group.class = edu.internet2.middleware.grouper.hooks.examples.GroupUniqueNameCaseInsensitiveHook

hooks.stem.class = edu.internet2.middleware.grouper.hooks.examples.StemUniqueNameCaseInsensitiveHook