Merge branch 'bones_was_here/improve-serverbench' into 'master'

Merge branch 'bones_was_here/improve-serverbench' into 'master'

Improve serverbench command WRT #273

- Use a temporary directory for the files previously created in the repo with -nohome (eg lock, data/data/defaultSVQC.cfg). This is better than just deleting the files as it will still work if the files created change, and won't annoy a user who is running their normal server or client with -nohome.
- Gitignore the temp directory, so it won't get committed if the serverbench was interrupted.
- Use dedicated instead of requiring it as an argument, previously without args it would run in threaded server mode which is considered unstable and doesn't run properly in this useage.

Resolves #273

See merge request xonotic/xonotic!62