Server script to download the latest installer

As promised, I talked with enumag about the script and he sent it to me earlier today.

You can access it at http://07th-mod.com/installer.php

By default, it will guess the user platform and get the latest stable release. You can force it to go through manually using: ``http://07th-mod.com/installer.php?system=win|mac|linux&branch=pre|stable``

Example: http://07th-mod.com/installer.php?system=linux&branch=stable

Beware that using ``branch=pre`` will only work if the most recent release is marked as a pre-release. If the most recent is a stable release, it will get the stable instead of the pre-release.

Right now the guessing part doesn't work, but I believe it is because of the current changes ongoing at the releases page. Earlier today it was working fine, so it might fix itself soon enough.

Lo script è ospitato su http://07th-mod.com/installer.php e interagisce con le release di GitHub. Inizia esaminando la logica lato server esistente per il rilevamento della piattaforma e il recupero delle release. Comprendi come determina i rami 'stable' vs 'pre' e si integra con la pagina delle release del progetto. Testa l'endpoint con diversi parametri di query per verificare il comportamento attuale e identificare il problema di indovinare.

Scritto dal modello di indicizzazione a partire dal testo della issue.