Underworld

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Documentation:
* Darcy flow models.
* New NCI Raijin build recipe.
* Many new models and tutorials.
* Cheatsheet added.

Enhancements:
* Docker usage no longer requires tokens.
* KSP convergence status now captured in python interface.
* `solve()` method now displays warnings for floating point over/underruns.
* Many general enhancements to visualisation.

New Features:
* New features for `min_max` function.
* solHA added.

API Changes:
* `min_max` function no longer accepts vector functions
by default, with instead a fn_norm function having to
be provided by the user.
* Neumann condition now takes `indexSetsPerDof` parameter instead of `nodeIndexSet`.

Bug fixes:
* Catch out fortran ordered numpy arrays when using `evaluate()` method.
* Parallel isosurface visualisation fixed.
* Corrected sampling for FieldSampler visualisation object.

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Enhancements:
* Improved swarm reload times for parallel simulations.
* Efficiency improvements for large proc count (>128) parallel simulations.
* Faster algorithms for swarms with deformed mesh.
* Many updates to visualisation routines.
* Compressible Stokes general improvements.
* New example models and analytic tests.
* Addressed numerous memory leaks (some minor ones still exist).
* Improved error handling, documentation & testing.


New features:
* User provided pre-solve callback function.
* Updated or new vis objects: Isosurfaces, contours, discrete colourmap.

API Changes:
* Neumann condition change in user provided stress function.

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Bug fixes:
* Critical bug fixed where retrieving symmetric tensor in 3d returned 2d result.

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Documentation
* Updates to make api documentation available via read the docs: http://underworld2.readthedocs.io/

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Enhancements:
* Improved function evaluation efficiency.
* Handle numpy int types in index sets correctly.
* Webgl figure saving.
* General visualisation enhancements.
* Better testing for visualisation.
* petsc 3.7 compatibility

New Features:
* ParticleFound function. Allows for 'sparse' swarm operations.
* Figure copying functionality
* SurfaceOnMesh visualisation object

Documentation:
* HTML api documentation.
* Big docstring updates.

Deprecated:
* 'swarm' parameter now removed in favour of 'voronoi_swarm' parameter.

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* Bug fix for the stokes system's psuedo incompressibility