Fix Emitter editing

[steffen-wilke]

Currently, the dialog that allows editing emitters in the utiLITI editor has some major issues:

• UI-wise the elements are misaligned and some are not fully readable (see screenshot) this makes the UI hard to use and understand
• When trying to create a new emitter from scratch in the editor, this doesn't seem to be possible at the moment; at least I wasn't able to get a visible result.
  • Some investigations showed, that a lot of ParticleParameters are not serialized properly (maybe unchanged values, especially the max values are not set as custom property?)
• I would say that this feature is entirely broken right now, unless you have an already working emitter and just want to tweak some numbers.
• When adding a new emitter, we should define appropriate default values so the user can already see something

We might also think about integrating these settings from the separate modal dialog to the normal PropertyPanel in order to enable live feedback on the changes in the editor and reduce the friction to play around with Emitter settings.
Alternatively, there should be at least a preview of the emitter in the modal dialog.

[nightm4re94]

Some more requirements:

• Exporting Emitters as xml
• Making Custom Emitters usable as EntityEmitters

[nightm4re94]

To make the whole editor component less overwhelming, we could consider an approach similar to Unity's Particle System Modules, where you can toggle behaviours such as velocity over lifetime / size over lifetime separately.

Being able to hide modules makes this a clean alternative to how our emitter panel looks.:

[nightm4re94]

In my recent Branch, I am redesigning the Emitter modification process in utiLITI from scratch.

[nightm4re94]

The new panel also needs to contain controls for particle rotation as requested per #345 .