Use VERSION env. variable or current timestamp for test builds
Ignore malformed polygons
Fixed an issue which caused us to traverse the entire tree for OpenCSG rendering traversals, where we didn't actually use the traversal results (for all nodes requiring CGAL)
removed unused member variable
bugfix: previous commit broke debug builds
Add diameter variable to the sphere, cylinder and circle primitives (fixes #392).

When doing the lookup, the diameter value has priority so if both diameter
and radius are given, the radius value is ignored and a warning is printed.
Extend sphere tests to cover the new diameter parameter.
Add cylinder tests to cover the new diameter parameters.
Extend circle tests to cover the new diameter parameter.
Merge pull request #509 from t-paul/issue392

Add diameter variable to the sphere, cylinder and circle primitives.
Updated eigen, gmp, boost, cgal and glew
updated Sparkle
child() deprecated for children()
update child example
refactor expr for range