Fix major loading time problems. When there are more than 3 contexts, loading...

Fix major loading time problems. When there are more than 3 contexts, loading time just to get the list was huge:

- Move YML file search and loading code to new method loadAllContexts() method that runs on Provision::__construct().
- Ensure dependent contexts can be loaded (using loadContext() method).
- Refactor objects to always be "ProvisionAware".
- Remove static functions for public and private.
- Fix ContextNodeDefinition to use ProvisionAwareTrait.