Rewrite ActionsLoader to use the executor system

[ghost]

Currently, ActionsLoader is inconsistent with the rest of the loader replacements. It uses a switch statement to check an element's type instead of the much more extensible IExecutor, which is used by all of the other loaders.

What should be done:

• Add executor interfaces to ActionsLoader.
• Rewrite LoadActionSets and ReadAction to use said executors.
• Optionally rename ReadAction to LoadAction for consistency with other method names.