Revert "remove Gaufrette as a submodule"

This reverts commit 61da071b14282be7443512841d4b2a886cbd8352.
Revert "remove the config folder from composer.json"

This reverts commit 12a444d98f5d17e5bdc98109cc85c076f67abbd7.
Revert "explicitly state the path for knplabs/gaufrette"

This reverts commit ffa6480276120d5f97882e12ba42e71a530df536.