add melt material model with latent heat

fix some bugs

indentation

clean up and add documentation

add some documentation

add two tests
add new line
Make sure the solution satisfies hanging node constraints after solution transfer.
Make it compile.
Address Timo's concerns about code.
Add some commentary.
Fix description at the top.
Describe what the test actually does (the previous description was simply wrong).
Merge pull request #142 from jdannberg/melting_model

Material model that includes latent heat of melting
Update test results.
Re-sort a few statement. Make sure we also distribute() the mesh
velocity vector.
Re-indent a couple of lines.
Leave a TODO.
Make test compile.
Merge pull request #145 from bangerth/fix-test-using-c++

Make test compile.
fix steinberger test output
Merge pull request #144 from tjhei/fix_steinberger_test_output

fix steinberger test output
update test output (verified, was just forgotten)
Add a new ConstraintMatrix to keep the mesh conforming on redistribution with a free surface
Merge pull request #4 from ian-r-rose/fix-solution-transfer-with-hanging-nodes

Add a new ConstraintMatrix to keep the mesh conforming on redistribution