added another way to retrieve some internal faces:
  now one can get all the (internal) faces (with the associated
  dof) that live on a given plane --defined by (a,b,c,d) s.t.
  ax + by + cz + d = 0.
working on putting all this into an external class.

* allow to set problem data from data file
* use uniform velocity instead of vortex
* handle boundary conditions (Dirichlet all over for the moment)
* do not fall in round off error trap for counting iterations
* save mass before and after reinitialization

* turned function sphere into static method sphere::phi

* small documentation bugfix

* access now private data members of HyperbolicSolver through accessors
* reformatted

* made all data private and provide const accessors where needed
* moved public CurrentFE& fe() from LevelSetSolver to HyperbolicSolver
* added protected non-const accessor to unknown function for LevelSetSolver

(protected _M_BCh_u -> private _M_BCh_fluid)

  in order to allow reinitialization to influence vectors in bdf
* initialize _M_t as well

all BCs now use BC Vector Interfaces member in FSIOperator class. Next step is moving all BCs declaration to the boundaryCondition.hpp file

BCs can now be defined outside the FS operators. Next step is to finish moving old dofInterface formulation for all FS operators to see if everything works fine. Then, every BCs will be moved to the file boundaryConditions.hpp in the test_fsi folder.

this should fix your problem Gilles

use program_options from boost 1.32 but make it optional