Support taking components of primitives.Nabla
Print better error message for S' in volume
Use parentheses in stringifier for NumReferenceDerivative
Use two-sided QBX for *any* PV/FP operator
Introduce conj, abs as functions
Remove MEMO file, FIXME comments do the same thing
Make sym.normal() an exterior normal
Tweak example, show kernel derivative
Introduce VectorVariable
Make Discretization.norm() work for vector quantities
Improve geometry plotting in test_ellipse_eigenvalues
Add initial (non-working) version of integral identity tester