VOFTools 3.2: Added VOF functionality to initialize the liquid volume fraction in general convex cells

An updated version of the VOFTools library for convex geometries is presented to add a functionality for volume fraction initialization, which is important for any VOF (volume of fluid) method. The earlier version of the library includes efficient analytical and geometrical routines for area and volume computation, truncation operations that typically arise in VOF methods, area and volume conservation enforcement in PLIC (piecewise linear interface calculation) reconstruction and computation of the distance from a given point to the reconstructed interface. The updated version incorporates an accurate initialization procedure, based on local grid refinement, to determine the liquid region bounded by a convex polygonal or polyhedral cell and a given implicitly-defined liquid interface. Also, two bugs have been fixed. 2D and 3D tests are provided in the software package to assess the accuracy of the implemented initialization procedure.