Started on the pack downloading system
Merge remote-tracking branch 'upstream/master' into modpack_downloading_system
Created basic modpack support
Added ModPackVersionDescription, DefaultModPackVersionDescription & implemented methods
Merge remote-tracking branch 'upstream/master' into modpack_downloading_system
refractored ModpackGuiPanel & added constructor for Modpack
Moved CacheManager to its own package & added a method for lazy loading of images
Updated interface CacheManager
Changed contract of CacheManager

A cache manager accepts a DownloadLocation instead of a normal URL now, this because a cache manager should check the file by itself
Updated ModpackManager to use ModpackListingDownload object instead of plain DownloadLocation objects
Use Map<String, ModPackVersion>  instead of List<ModPackVersion>
Added .getName() to UnresolvedModpack's
Added priorities to DownloadLocation's
Added missing license to all updated files
Updated ModpackManager, works now
Added cache system for files
Merge branch 'master' into modpack_downloading_system
Merge branch 'modpack_downloading_system'