Pushing gui_types into separate modules

[Toma400]

During pre-alpha 3 development, I quickly saw how enormous gui_types become because of putting all GUIs of the game in one place.
This was a thing I was thinking about for long to simplify, and eventually both my thinking and practice proved to be working - so I separated load.py from gui_types and made it working via such simple means.
Right now, other non-publicly-playable menus are built on this system, but the old ones are still in the same place.

Which is why this issue is made - all gui_types contents that are GUI building should be moved eventually to separate modules, so it is much cleaner to read GUI code.
With character creation or settings, where multiple layers of GUI are used, there should be decision whether to keep them together (bulkier variant) or separate each "second layer" type of GUI.