start working on tao-in-petsc.
fix issues on enable_petsc_tao and updating demos and tests
remove FindTao cmake module
tiny fix
add Neumann and Dirichlet bcs to demo-dg-poisson
change n and h in Poisson.ufl
Remove identifiers beginning with an underscore and an uppercase letter (fixes issue #134).
Merge branch 'johannr/fix-issue-134' into master.
Add set_diagonal (with GenericVector) to GenericMatrix
Merge branch 'master' into johanhake/topic-set_diagonal
Add deprecation warning to construction of symbolic geometric quantities from a ufl.Cell, should now pass the mesh.
Fixes for changed naming of backend matrix in master
Refactor Function.__init__ to make it clearer what happens. Now every case has its own __init_foo function which separately are easy to understand.
Allow creation of function space from ufl.Domain. Refactor some of the shared analysis of the mesh argument to helper functions.
Some bugfixes and disable checking of constrained_domains which I now understand why was disabled before.
Pass count=self.id() to all ufl.Coefficient.__init__ calls.

Made sure that the cpp constructors are called first,
such that the id() should be valid.
Fix doctest for mixed-poisson-dual.
Switch criterion for resetting sparsity by
assember from A.size(0) == 0 to A.empty().

Fix implementations of GenericMatrix::empty().

Ensure that GenericMatrix::compressed() does
not silently pass without setting values for
targets without sparsity pattern.
Deprecate AssemblerBase::reset_sparsity.
Small fix for ML pc via Trilinos (left -> right preconditioning)