FSPL (i.e., FFP) with limb darkening

[rpoleski]

If somebody is working on events with large rho, single lens, and limb darkening, then please have a look at the branch Version3_1vbbl: https://github.com/rpoleski/MulensModel/compare/Version3_1...Version3_1vbbl I've implemented there import of VBBL for point sources. It's a kind of dirty way (file with interpolation coefficients is pasted into .h file) but works well and fast. And much faster than Lee09 method.