CMakeParseArguments: Remove superfluous includes of CMakeParseArguments

Because cmake_parse_arguments() has been implemented as a native command, there is no need to include(CMakeParseArguments) anymore. Its inclusion has been removed from several CMake modules.

Tests/CMakeOnly/CMakeLists.txt has been changed to include the building CMake's copy of CMakeParseArguments rather than the built CMake's copy. This file included the built copy because when this file was introduced, CMake could still be built with versions that didn't supply cmake_parse_arguments(). Now, CMake requires 3.1 or greater, where cmake_parse_arguments() existed but was still in the form of a module, so we include it from the building CMake.