API Make Object::config use late static binding

Can now be used in instance scope, like:
  $this->config()->db
and in static scope, like:
  Page::config()->db
Cache the merged version of any Config value in an in-mem LRU cache
Extract statics via code analysis rather than introspection
Add ability to create temporary Config copies
FIX DataObjectSchemaGenerationTest trying to modify config statics directly