render: s/Render/RenderWorld/g.

To differentiate from RenderUi (coming soon).
Keep current map view in World.

We can't use sf::RenderWindow's internal view for that if we want to use
it for other purposes (as in making the UI immune to scrolling the map) too.
fileutils: log filename on a CHECK.
Preliminary UI.

Doesn't do much for now, but should be a good basis for implementing
something actually useful.