Enhancement: Use mesh gradients for bitmap tracing

PROBLEM: Currently the Inkscape Trace Bitmap algorithm generates only a group of paths to reproduce the original image. The coming new and improved algorithm seems to do the same. But sometimes paths are not enough because most realistic images have surfaces made of continuous color gradients not of monochromatic distinct areas.

SOLUTION: Add to the Trace Bitmap algorithm the option to generate a Mesh Gradient when the image region to trace is not of uniform color, and generate group of paths for boundaries and all other image regions with uniform or sudden changes in color. The mesh gradient will be generated creating the nodes on all the inflection points (stationary, turning, saddle, etc.) of the 3-dimensional function mapping each of the 3 color channel (RGB). The three resulting mesh gradients will be then merged and in case of almost matching node positions, the nodes would be merged and the color values added.

SCREENSHOT: http://www.inkscapeforum.com/download/file.php?id=3525