Composer support related changes. These are being included for testing.

Add cusomization of composer.json to support module-installer-plugin during install

Add checks for OpenSSL and JSON to installer, as those are needed for composer. JSON is normally part of PHP, but due to an odd clause in its license, some distributions (such as debian and derivatives) package it separately.

Add a composer.phar to xoops_lib.

Add Xoops\Core\ComposerUtility.php that provides a mechanism to invoke composer to run commands under program control.