Add functions to generate scenegraphs in json for the three.js renderer

close 3d cylinders

Add support for three.js mesh=True keyword

get threejs implicit_plot3d objects working

Add support for n-sided faces in index_face_set scene trees.
3d lighting capabilities

import lights into global namespace and adjust default lighting schemes

lighten up default lighting a bit for 3d graphics

Add support for three.js light helpers
Change EMBEDDED_SAGE to a dictionary

Modify show routines for the sage cell server

Update patches for version 2 of the sage cell server
Use new display system for displaying sagecell-specific things

Some things are still not quite right in this system:

1. there is confusion about whether data or filenames should be passed into handler functions
2. perhaps we shouldn't use mime types, but should just have an image handler, a jmol handler, etc.
Make GSL random distributions initialize with the sage random state functions

This means that Sage's randstate set_random_seed function will make the
GSL distributions also be predictable (for doctests, random matrices, etc.)
Delete #random on some matrix constructor doctests that now depend on Sage's random state