…mands

Previousely when attempting completion for commands `module:enable`,
`mmodule:disable` and `module:uninstall` and error would be disaplyed,
stating that "magento" was not found.
Upon inspection of the issue in the related completion script it became
clear that:
1. The shell command `magento` does not exist as the CLI script of
   Magentoresides under `bin/magento`.
2. The module aggregation would not work after referncing the
   appropriate CLI command as an undeclared variable was being
   introspected.
3. Using Magento's CLI command took too long to respond as it has to
   bootstrap the whole Magento stack in order to deliver modules.

Thus the whole aggregation was rewritten to a form that actually works
and reduces the aggregation to reading the appropriate information
directly from the configuration file, provided that the file exists and
PHP is installed.

…commmands to not use PHP script

Executing random scripts from fish completion poses a threat to the
system. While this would indicate that the Magento installation has been
corrupted, it still is better to not run `app/etc/config.php` to get
hold of the modules.
Thus the module aggregation was rewritten to make use od `sed` instead,
which has the additional benefit of being faster than using PHP.

…d `module:status`