Set server threads as daemon

[ryuukk]

This has always been an issue, serve-d would never close dcd-server processes

This was because server threads was not marked as daemon, so the OS would never close dcd-server process whenever the Text Editor would close serve-d process

Fixes #334 and #336

[ryuukk]

Actually no, it still seems to be random, sometimes it closes it, sometimes not, there might be something else stuck