General (pretty obvious) UI enhancements

While I like the Output, I dislike the UI.
In my point of view, the following topics are only UI-related (and pretty easy to implement)

*) Preferences/Max Processes
→ ALWAYS Keep ONE extra process to support UI interactions (render n-seconds)
→ this shall actually be renamed to ‘max Encoding processes’
(separate Task-Queues for Encoding and UI-preview)
*) allow us to pause all pending encoding tasks
- needless to say: ‘resume/remove/abort pending tasks’