Better output in headless mode

[ShirleyNekoDev]

The output log while loading a scene (and therefore loading octree, regions, entitites, chunks, ...) might confuse some users, because it does not always update its progress after completing a specific step.

Some things I'd like to work on:

• reworking the task tracker and progress tracker to be used in GUI and log (very tightly coupled to different systems right now)
• flag to disable headless output refreshing (not overwriting the last line of output, therefore creating new lines every time something happened)
• fixing inconsistent log spacing, messages and errors