Documentation:
 * add an overview for each module.
 * add an example for .all() and Cwise::operator<

To try it with the unit tests set the cmake variable TEST_LIB to ON.

-fix CMakeLists, public headers weren't getting installed

extended cache optimal product to work in any row/column
major situations, and a few bugfixes (forgot to add the
Cholesky header, vectorization of CwiseBinary)