* CMake modifications and Config file generation
* CMake minor style changes
* Get rid of commented lines, fix indentation
* Respect Windows conventions for CMake config directory, Fix error with Config Version file, Export CMake package
* Add CMake option for use of ENTT_COMPILE_OPTIONS, Add CMake option for using libc++, Remove from EnTT target and move it to test targets
* Fix indentation
* Fix indentation (again)
* Fix Windows problems with compile option -Wall in not using it on Windows
* Improved generator expression
The problem with -Wall is not due to the platform but due to the compiler MSVC
* Set compatibility for ConfigVersion file to AnyNewerVersion, Add PATH_VARS CMAKE_INSTALL_INCLUDE_DIR of configure_package_config_file, Remove redundant options, correct target_include_directory for INSTALL_INTERFACE, set the Version in EnTTConfig file and check CMake version
* Add missing closing brace, Add a special config file for the build tree
