Add SphereMesh and EllipsoidMesh classes.
Use new ellipsoid/sphere generation in demo and add unit tests.
Rename show target in FindTAO's temp Makefile

The temp Makefile includes $TAO_DIR/conf/tao_base which
itself defines a target named 'show'. This introduces
a conflict.
Add simple interface to build unstructured meshes of ellipses.
Check that CGAL is available in demo for generating unstructured ellipse meshes.
Add ellipse and ellipspoid meshes to demo.
Documentation updates for mesh generation.
Get doc tests to pass.
Merged in optimizer/dolfin/findtao (pull request #57)

Rename show target in FindTAO's temp Makefile
Merge branch 'garth/sphere-circle-meshes'
Fix broken call to dolfin_error when building without CGAL.