Add multi instance support by optionally passing a -c <file> flag

Allows to pass a configuration file to configure multiple shopware instances on one machine:

    ./sw4-cli-tools -c /path/to/shop.ini
    ./sw4-cli-tools -c /path/to/other-shop.ini

Also added three flags to directly perform operations:

    -i Install
    -d Install Demo Data
    -k Clear Cache