Adding a class *LagrangeInterpolator* that interpolates a GenericFunction fast onto a Lagrange function space.
Changing order of arguments in interpolate and adding unittest to /test/unit/test.py
Adding dolfin_assert where appropriate and using const for STL iterators. Fixed conflict in unit/test.py
Merge branch 'mikael/lagrange-interpolation'
Use ugly double square brackets to fix MathJax problem (fixes Issue #163)

Problem is that MathJax does not support \llbracket and \rrbracket