Basic functionality for NuKnossos

[ngld]

• [x] list mods
• [x] download & install
  • [x] fetch metadata for installation (dependencies, download links, checksums)
  • [x] resolve dependencies
  • [x] download archives
  • [x] extract archives
• [x] launch FSO
• [x] FSO flags
• [ ] FSO settings
• [ ] verify file integrity
• [x] update Knossos
• [ ] update mods