discretefunction with child function

See merge request !134

DiscreteFunction vs. DOFVectorView

See merge request !125

Simplify observer

See merge request !131

removed dependency on dune-functions interpolate due to breaking changes

See merge request !133

removed dependency on dune-functions interpolate due to breaking changes

See merge request !130

Issue/cleanup concepts

See merge request !128

no-mpi issues in PETSc backend

See merge request !129

added check to add_amdis_executable that chosen Grid exists

See merge request !127

replaced implementation of static Size template with generic constexpr function

See merge request !126

cleanup of headers and itl solvers in mtl backend

See merge request !124

removed some forward declarations from GlobalIdSet

See merge request !123

Optimize compile builds using ccache and gold linker

See merge request !122

fixed no-mpi bug in istl backend

See merge request !120

No-MPI build with PETSC backend fixed

See merge request !121

dune 2.7 updated some preconditioners in istl such that some precompiler files had to be fixed

See merge request !119

Rewriting adaptive grid

See merge request !117

cleanup wrap_or_share

See merge request !116

Feature/observer

See merge request !79

Major changes:
  Add wrapper class AdaptiveGrid<Grid> to be used instead of a
    dune-grid within AMDiS. This provides most of the grid interface
    and supports automatic updates of bases.
  Change: MeshCreator now returns an AdaptiveGrid
  Change: ProblemStat uses AdaptiveGrid internally and returns an
    object of that type
  Add class ParallelGlobalBasis<Basis> as a replacement for a
    dune-functions basis. This implements the complete interface and
    can be used as a replacement for a regular basis in all contexts.
    It supports automatic updates.
  Add free function makeGlobalBasis to make a ParallelGlobalBasis
  Change: AMDiS basis creators now return a ParallelGlobalBasis
  Change: ProblemStat uses ParallelGlobalBasis internally and returns
    an object of that type
  Add classes Observer/Signals. Classes can derive from those to take
    part in the automatic update feature.
  Add update(Event const& e) methods to classes using the feature
    above. They implement the action to be done when the registered
    Event is triggered.
  Remove GridTransfer[-Manager] and replace with the new
    Observer/Signals implementation
  Change: linear algebra communicator is now a part of
    ParallelGlobalBasis
  Add wrapper for DataTransfer objects that can be used instead of a
    base class pointer and performs deep-copy operations on copy
    construction and assignment
  Change: DOFVector DataTransfer member is now stored using the new
    wrapper class DataTransferWrapper
  Change: preAdapt, adapt, postAdapt callbacks are now called after
    calling the respective grid function. Classes that previously used
    any of them had their methods changed accordingly.

Minor changes:
  Remove Comm argument for ctor of [Bi-]LinearForm, DOFVector
  Change ctor argument from Comm to Basis in
    linearalgebra/<impl>/[Matrix-, Vector-]Backend.hpp
  Simplify DOFVector copy/move by defaulting
  Remove DOFVector::resize override
  Remove DOFVectorInterface.hpp
  Change: linearalgebra/Traits.hpp includes the backend-specific
    Traits file. This is required to break an include loop.
  Add global 'solver category' initfile parameter used by the ISTL
    backend communicator when no parameter  at prefix + '->category'
    is found
  Fix commented out parts in DOFVectorTest, DiscreteFunctionTest
  Add unit test for Observer functionality
  Add helper function wrap_or_share (see amdis/common/SharedPtr.hpp)
  Fix backend = ISTL check for ISTLCommTest in CMakeLists

Disable tests for PETSc with nonmatching type

See merge request !115

Cleanup the constructors of MatrixBase, VectorBase, BiLinearForm, and LinearForm

See merge request !113