Some improvements

* Added contributors list to `composer.json` (linked to github contributors graph)
* Improved Behat context
* Fixed/Cleaned/Tested configure options handling
* add `--default` option to `install` command
@stof This info are parsed from either config.m4 or config.w32, which contain different options most of the time. They were currently part of the json but it is pointless as we can just fetch them on install. Also my last patch separate them already, one for windows and one for linux.