Add support to pick+choose PHP extensions via the installer

[hopeseekr]

Give the Installer an Advanced Mode that gives users the option to manually specify what PHP extensions they wish to utilize.

This will put us in direct competition with www.phpdocker.io.

[hopeseekr]

This just needs documentation at this point.

All the user will have to do to this now is

    php vendor/phpexperts/dockerize/install.php