ResourceFactory: Move available function to platform

refs #5514
Class doc for ResourceFactory

refs #5514
Class doc for Platform

refs #5514
ResourceFactory: Add function create(<name>)

The ConfigAwareFactory is an interface forcing "backend-type" classes to call
ResourceFactory::createResource() passing a config they got in the constructor.

That's kind of overdesigned, if the ResourceFactory wants to be something like
a service locator it's responsabilities should include object instantiation.

refs #5514
ResourceConfig: Chance createResouce to create

Not useful everywhere. Changed on the best suitable places.

refs #5514
Platform: Drop *Available function

Create a function extensionLoaded and change usages.

refs #5514
LdapBackendFormTest: Fix mock

refs #5514
Merge branch 'bugfix/ConfigAwareFactory-5514'

fixes #5514