Fix MoO2 subdirectory bug + remove sockdrive references

- Fix flattenSingleDir: flatten when exactly 1 root directory exists,
  even if other metadata files (file_id.diz, *.nfo) are present at root
- Fix buildDosboxConf/buildJsdosJson: add 'cd <dir>' before executable
  when it lives in a subdirectory, since DOS treats '/' as switch char
  (previously 'mastori2/ORION2.EXE' was parsed as command 'mastori2'
  with switch '/ORION2.EXE')
- Remove SockdriveResource.java entirely
- Remove bundleType field from Game.java (was 'standard'/'sockdrive')
- Simplify GameResource.java download endpoint
- Clean up upload resource

README.md

@@ -61,7 +61,6 @@ java -jar target/quarkus-app/quarkus-run.jar
   "year": 1993,
   "genre": "FPS",
   "developer": "id Software",
-  "bundle_type": "standard",
   "bundle_file": "doom.jsdos",
   "has_cover": true,
   "ready": true