Avoid child dependency installs

[nilmerg]

closes Icinga/ipl-scheduler#49

[nilmerg]

Doesn't work yet. Autoloading is messed up. Composer usually takes care of dependency resolution during autoloading. But by faking them here using the repl/acer library, composer thinks they are available. This then leads to problems with e.g. ipl/scheduler which contains a file autoloader that expects a particular dependency being available while it runs. And it runs right away if Icinga Web requires the ipl's vendor/autoload.php. (Which might happen before icinga-php-thirdparty's autoloader is required)

We need our own dependency resolution for libraries. ipl could define the following in composer.json:

  "extra": {
    "icinga-load-order": {
      "after": ["icinga/icinga-php-thirdparty"]
    }
  },

Icinga Web parses this and makes sure ipl is only loaded after icinga-php-thirdparty. Or so.

[nilmerg]

And no, changing ipl/scheduler file autoloader doesn't help.