GitLab

* FlowParameters will serve as interface to the operators
    * It also manages storage and access of parameters
* RichardsParameterization is the base class for all parameterizations
* MualemVanGenuchtenParameterization is a derived class defining all
    necessary parameterization functions and stores the parameter values

Resolve "Add additional debug job with Clang"

Closes #69

See merge request !54

Specify compilers through build-arg CC and CXX of Dockerfiles

* Split setup CI stage into two jobs for GCC and Clang
* Add compiler (CC) as ARG in Dockerfile
* Remove dune-env-clang.dockerfile

[ci skip]

Based on regular (GCC) DUNE env image

Resolve "Update to DUNE v2.6"

Closes #68

See merge request !53

Target builds a derived class of Simulation and will hence emit all
warnings

[ci skip]

Concerns parallel_reference_compare test

* Raise DUNE versions to v2.6
* Raise dependency versions to packages included in Ubuntu 18.04
* Remove badges
* Fix 'docker build' command with path to Dockerfile
* Update installation instructions for Ubuntu
* Move interactive Docker session further down

* Set blocking sizes for vector backends
    - QkDG is falsely set to 1 due to runtime error
* Use namespace PDELab::ISTL instead of PDELab::istl
* Use new MCMGMapper constructor with layout functor
* Use Dune::GeometryTypes for FEM construction
* Remove includes of deprecated header
    <dune/pdelab/common/referenceelements.hh>
* Fix bug where MatrixBackend in AdaptivityHandler would store entries
    per row as double

This reverts commit 3de62db0.

This reverts commit 2971b6d1.

This reverts commit 8185d6fe.

This reverts commit ab886d7b.

* Update .gitlab-ci.yml for new image version 2.6
* Update branches to check out in dune-env.dockerfile

Resolve "Apple Clang on Mac OS Sierra compiles DUNE, but not DORiE executable"

Closes #28

See merge request !51

* Clang is now supported alternative to GCC
* Remove export of CC and CXX variables for macOS

This makes the source code compatible to Clang.

Adapt CI pipeline to 7 multi core CPUs

See merge request !49

Resolve "Add job for building and deploying DORiE Docker image"

Closes #56

See merge request !47