Implement a geodetic buffered LineString

We've already got a BufferedLineString but it isn't geodetic.

A geodetic version could be implemented structurally similarly: It could be an aggregate of buffered lines. And each buffered line is the intersection of a perpendicular pair of infinite lines that are buffered. An infinite line on a sphere is a complete ring around the globe that cuts it in half. So most of the work here would be re-imagining the InfBufLine class in a geodetic way; the rest should hopefully more or less fall into place, maybe even re-using code after some refactoring (but don't worry about re-use at the moment as it may be distracting).

Start by locating the existing BufferedLineString and InfBufLine implementations and tracing how buffered lines are aggregated and intersected. Define the geodetic equivalents for spherical infinite lines and perpendicular buffered lines, then verify that the resulting geodetic LineString follows the proposed structure and behavior.