Added CreateActionExecutor.
Refactorized interface ActionExecutor.
Added basic tests and some error tests.
Added tests for CreateActionExecutor.
Avoid executing executors before validating or with validation errors.
Added DeleteActionExecutor.
Refactored UpdateActionExecutor.
Added DeleteActionExecutor.
Refactored UpdateValidationExecutor.
Completed test to detect facts that must remain after a delete action.