add --prefer-lowest and --prefer-stable to update command

Run `composer update --prefer-lowest-stable` and get all the deps installed to their lowest (pretended) supported version

Fixes #3440
Fixes #1902
Sure, basically the same as https://github.com/composer/composer/pull/3101/files + https://github.com/nicolas-grekas/composer/commit/4bd748b4630d01e3c268a941f748d0c317b7a156 which fixed some mistakes :)