Leave todos.
Merge branch 'master' of github.com:geodynamics/aspect into compressible_perplex
Update steinberger material model to run with the new material model interface (calling also viscosity for the creation of the adiabatic conditions).
Add experimental support for compressibility in the steinberger material model.
Merge branch 'gplates_cookbook_patch' into compressible_perplex
Added functions to simulator access that return the surface pressure input parameter.
Small bugfixes in lookup class of steinberger material model.
Changed steinberger material model to new interface. Made the incompressible formulation consistent and added a compressible formulation.
Viscosity is now only called if adiabatic conditions is available. No need to check for that in function any more.
Rename some variables for clarity.
Merge branch 'master' into compressible_perplex
Change the simple-compressible test to a more reasonable initial condition.
Made steinberger material model aware of $ASPECT_SOURCE_DIR.
Made reference viscosity a user input parameter for steinberger material model.
Document reference viscosity. Set default to old value. Cleanup.
Add a test for the steinberger material model.
Add a test utilizing the simple material model for comparison purposes.
Add a test for the incompressible branch of the steinberger material model.
Reverted typo.
Renamed functions and left comments to try to explain the steinberger model.