Refactor to factory paradigm

[alxdncn]

This is a refactor to improve stability and scalability of new features.

[regcs]

Status of the Refactor

General

• Add a log file mechanism
• Shift the add-on preferences to a separate file (preferences.py)
• Implement pyLightIO as an external package to handle the lightfield display communication
• Shift all UI related code to a separate file (ui.py)
• Handle installation of required python packages
• Include pyLightIO in the bundle (this will be changed in later versions to a pipinstall)
• Final code clean-up

Lightfield Viewport / Live View

• Remove freeHPC & lonetech's lightfield shaders from the code base
• Clean-up the codebase of the Lightfield Viewport
• Use HoPS via pyLightIO for the Lightfield Viewport: The separate Blender window is gone.
• Re-implement the quilt viewer
• Remove holographic / lightfield cursor (see Product definition for lightfield / holographic cursor #49)
• Re-implement multi-scene handling (currently the lightfield viewport shuts down on scene changes / creation)
• Handle lightfield viewport behavior when no camera is selected: Request displaying the LG demo quilt from HoPS

Quilt Renderer

• Remove redundant code parts for file naming
• Optimize operator logic for flexibility and to enable additional implementation of the multiview camera systems

[regcs]

Everything I wanted to refactor for version 2.0 should be done now. I am sure, there are other areas that still can be improved in the code base, but I leave those for the future.