v1.3.0 beta

• Added plugin-system
• Added scheduled backups (enabled by default)
• Added backup restore functionality (--restore flag)
• Added server watchdog @bennydiamond
• Added setting low-priority of render-processes @bennydiamond
• Added timeout for UpdateChecker HTTP-requests
• World-name now loads from server.properties instead of configuration.json
• Several fixes & optimizations @tomrhollis
• Fix application exit on stop command