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
Some micro-optimisations for Config
Add some tests for the static parser
Remove debug message, any still unexpected token is an error
FIX Avoid get_parent_class in ConfigStaticManifest (was loading all classes)
FIX Static polution with informational fields
Merge pull request #1244 from silverstripe-rebelalliance/feature/config

Feature/config