Ufl

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- Added nabla_grad and nabla_div operators
- Added error function erf(x)
- Added bessel functions of first and second kind, normal and modified,
bessel_J(nu, x), bessel_Y(nu, x), bessel_I(nu, x), bessel_K(nu, x)
- Extended derivative() to allow indexed coefficient(s) as differentiation variable
- Made ``*Constant`` use the ``Real`` space instead of ``DG0``
- Bugfix in adjoint where test and trial functions were in different spaces
- Bugfix in replace where the argument to a grad was replaced with 0
- Bugfix in reconstruction of tensor elements
- Some other minor bugfixes

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- Support c*form where c depends on a coefficient in a Real space

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- Add script ufl-version
- Added syntax for associating an arbitrary domain data object with a measure:
dss = ds[boundaries]; M = f*dss(1) + g*dss(2)
- Added new operators elem_mult, elem_div, elem_pow and elem_op for
elementwise application of scalar operators to tensors of equal shape
- Added condition operators And(lhs,rhs) and Or(lhs,rhs) and Not(cond)
- Fixed support for symmetries in subelements of a mixed element
- Add support for specifying derivatives of coefficients to derivative()

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- Remove set_foo functions in finite element classes
- Change license from GPL v3 or later to LGPL v3 or later
- Change behavior of preprocess(), form.compute_form_data(), form_data.preprocessed_form
- Allowing grad, div, inner, dot, det, inverse on scalars
- Simplify Identity(1) -> IntValue(1) automatically
- Added Levi-Cevita symbol: e = PermutationSymbol(3); e[i,j,k]
- Fix bug with future division behaviour (ufl does not support floor division)
- Add subdomain member variables to form class
- Allow action on forms of arbitrary rank

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- Allow jump(Sigma, n) for matrix-valued expression Sigma
- Bug fix in scalar curl operator
- Bug fix in deviatoric operator

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- Bug fixes in PartExtracter
- Do not import x for coordinate
- Add Circumradius to Cell (Cell.circumradius)
- Add CellVolume to Cell (Cell.volume)