Separated all of the member functions from the FSIProblem<dim> class.

Now there is:

assemble_ale.cc
assemble_fluid.cc
assemble_structure.cc
dof_mapping.cc
 - build the mappings, and both transfer functions
output.cc
 - compute errors and push solutions to vtk files
run.cc
setup.cc
 - both Dirichlet boundary conditions and the geometry setup and matrix initializations
small_classes.h
 - currently only contains the Info class
solve.cc
support.cc
 - contains build_adjoint_rhs along with interface_norm and interface_error