TODO split up in py-package and unreal plugin

[hannesdelbeke]

maya has 2 options for pyblish: plugin or py-package

• https://github.com/pyblish/pyblish-maya/tree/master/pyblish_maya
• https://github.com/hannesdelbeke/pyblish-maya-plugin

the current pyblish unreal, can't be used in batch mode without installing the UI.
but do we need this though? anyone who wants batch mode only, can just

• pip install pyblish-base,
• and register host unreal
  DONE