Add polyhedron example

Adds an example triangular pyramid polyhedron to the Basic 3D tutorial
Move tutorials 1 and 2 to new naming convention
Add 2D shapes and extrusion tutorial

Makespace logo DXFs courtesy of Makespace: http://makespace.org
Add programming constructs tutorial

TODO: Add more functionality. e.g. matrix and vector maths, more
detail on variables and scope, lookup & search.
Add 3D -> 2D projection tutorial

Yoda model from Cas Moor on Thingiverse. CC-BY-SA
http://www.thingiverse.com/thing:306539
Add surfaces tutorial

Also adds python script to generate 16x16 surface file from a text
file.

TODO: surface-from-png example is commented out because it causes a
crash on my system
Add libraries and include tutorial

Uses modules from MCAD