add special rules for landfill under curved and diagonal rails

[chriswa]

The existing landfill code uses bounding boxes defined by the size property of the blueprint's entity. Curved rails do not seem to have a size property, so no landfill is generated for them. Diagonal rails fit in a smaller space than their bounding box, which results in wasted landfill and a blocky appearance.

This PR adds a lookup table for special offsets for curved and diagonal rails which was generated by creating blueprints for each rail section atop (pruned) landfill in /editor mode using Factorio 1.1.59.

Before:

After:

Using Kitch's 2 Lane Rail Book - 3.2 on FactorioPrints

P.S. Thanks for the great web service! <3

[demipixel]

May take me a bit for this to be pushed out—dealing with some build issues.

[demipixel]

Should be live!