Test php project for DynamicReturnTypePluginTestEnvironment

Standalone project used in developing the DynamicReturnTypePlugin which covers areas of usage that can be problematic. To verify cases are covered PHPStorms inspections are run on the code in this project. If there are errors such as unknown method etc then plugin is broken.

Note project folder to open in PHPStorm now is TestEnvironment child folder so composer is excluded completely from inspections.