break out DEL/DEL0?

[mdsumner]

To solve the license issue.

The stuff is isolated to code in these files and these are self-contained from what I can tell

R/DEL-model.R
R/DEL0-model.R
R/polygon-finder-for-triangles.R
R/as.mesh3d.R

The as.mesh3d requirement might be called on elsewhere in the plotting, but all other examples are doc or actual examples.

anglr would go to GPL or MIT and conditionally Suggest another package.

[mdsumner]

A problem is the terrainmeshr wrapper, because that (MIT) could exist as a basic support - so maybe the extra package simply provide extra methods, and otherwise everything not allowing RTriangle is geared to rasters and path-triangulation.