Remove all occurences of @brief and @returns from PHPDoc

* test case added to avoid adding them later

@ringmaster Aaaand here it is.... Removed over 800 occurences of @brief (and some @returns) and added a test case to avoid a later regression for those.

This also will improve the text snippet in the generated API - ref #4883

cc @PVince @Xenopathic @DeepDiver1975 @butonic