Move the stub's geodesy into a renderer-neutral src/geo

WGS84, ECEF and geodetic conversions, surface normals and east-north-up
frames, as plain {x, y, z} objects, exported as ./geo. A test checks
them against Cesium over random points and the poles. The stub's maths
re-exports them and keeps only the camera angle conventions.

package.json

@@ -295,6 +295,7 @@
     "./tools/services": "./src/tools/services.js",
     "./view": "./src/view/index.js",
     "./agent/world-packet": "./src/agent/worldPacket.js",
+    "./geo": "./src/geo/index.js",
     "./render/contract": "./src/render/contract/index.js",
     "./render/stub": "./src/render/stub/index.js",
     "./render/conformance": "./src/render/conformance/index.js"