[keycloak-dev] Initial Client Storage SPI

[Bill Burke]

As part of Openshift integration, I needed to implement a Client
Storage SPI.  Here are my plans for it:

* It is a private SPI
* Only read only support.
* Only lookup support to facilitate client login and grants and stuff.
Listing all clients will not show up in admin conosle
* There will be no admin console support.  This means, no admin
console support for provider config.  Providers can only be configured
through REST API or realm import.
* Basically it will be bare bones to support Openshift integration only.

My plan is that Openshift support will be distributed as an extension
to our base image and/or, it will be a template realm.json import file
that users can edit.  I just don't want to expose an unfinished SPI.

I'll probably have a PR for review early next week.

-- 
Bill Burke
Red Hat