New documentation for development tools

docs/composer/plugin/d4d/index.md

docs/dev_tools/index.md

docs/files/screenshots/configuration_add.png

docs/files/screenshots/configuration_done.png

docs/files/screenshots/configuration_new_webpage.png

docs/files/screenshots/settings_php_add_server.png

docs/files/screenshots/settings_php_debug.png

docs/files/screenshots/settings_php_new_server.png

docs/files/screenshots/start_debug.png