Passes FC and F77 env vars when configuring Dune

Closes #146.

CMAKE_Fortran_.*  and environment variables related to Fortran are passed on
explicitly to Dune via the cache script DuneVariables.cmake. Since Fortran is
not a BEM++ languages (no enable_language(Fortran) in BEM), the variables
CMAKE_Fortran_.* will exist only if the user declares them explicitly.
Merge pull request #147 from bempp/rsdt/issues/146

Passes FC and F77 env vars when configuring Dune
Disables Fortran in Dune build

It is still possible to compile Dune with Fortran by passin
"-DENABLE_Fortran=TRUE" to cmake.

Closes #148.
Merge pull request #149 from bempp/rsdt/issues/148

Disables Fortran in Dune build
Clang formatted source files
checkConsistency() no longer requires rhs.dualSpace() to be defined. #150
Allow grid functions to have undefined dualSpace in solver.
Working on weak_form_hmat_assembly_helper.cpp
Working on hmat_global_assembler
Merged master changes into hmat branch
Started Hmat Options class
hmat_global_assembler.cpp compiles now.
Blockcluster generation compiles
Committed missing files.
Added new option structures for hmat
Updated file formattings
Updated Swig to fix C++11 compatibility
Updated formatting
Data Accessor class compiles
Working on HMatrix Compression