Specify floor textures

[codebot]

• allow (optional) specification of floor textures and texture-scales
• add some new textures
• fix polygon remove-vertex tool
• fix bug in floor generation when concave floor polygons were "losing triangles" during processing after intersection, since the Shapely library triangulation routine doesn't handle concave polygons and "post-intersection" with the original polygon is required to handle the concave sections. Left in some optional debugging stuff using matplotlib because it's basically impossible to debug geometry stuff without some plotting routines available.