ModManager: Have list() to return a list of all located filenames
FileParser: remove open(), have open<Description>() instead.
UtilsFileSystem: add pathExists and isDirectory
Replace open<Description> by openLocated
Rewrite ModManager::list to expand directories automatically
Implement new FileParser to work according to specified documentation

Signed-off-by: Stefan Beller <stefanbeller@googlemail.com>
FileParser: Rename open<*> to open again
FileParser: Do not crash when trying to continue reading new files
FileParser: Fix loading multiple files with one parser
EnemyGroupManager: Do not iterate mods manually, ask ModManager for a list
MessageEngine: Do use prepared mod list from ModManager
Merge remote-tracking branch 'mainline/master' into modmanagement
Merge pull request #637 from stefanbeller/modmanagement

Modmanagement