Export spherical coordinates of points outwith flat outline

[davidcsterratt]

Currently ReconstructedOutline$mapFlatToSpherical() drops input points outwith the flat outline, which causes problems when used as an API function. It would be desirable to enable points outwith the outline to be mapped to phi=NA, lambda=NA so that rows of the output correspond to rows of the input matrix P.

[davidcsterratt]

The above commit adds an option dropna to ReconstructedOutline$mapFlatToSpherical(), which is TRUE by default. To not drop the points outwith the outline, use the call ReconstructedOutline$mapFlatToSpherical(P, dropna=FALSE).