Add return statements to PetscErrorCode functions.
Add cases for 3-D flow over a flat plate.

 * Square flat plate, AoA 45 deg, Re 200 and 300.
 * Delete cases flatPlateRe200 and vortexShedding.
Add regression test for lid-driven cavity flow.

 * Associated inputs are in the folder tests/NavierStokes.
 * Edit makefile appropriately.
 * Use function initialize for FlowDescription & SimulationParameters.
 * Change member permissions to public in the solver classes.
 * Edit .gitignore.
Merge branch 'develop' into petsc-3.5-compatible
Edit the rule for running tests.

 * The rule now both compiles and runs the tests.
 * Add flag to compile c++0x to the makefile in src/solvers.
Merge branch 'develop' into petsc-3.5-compatible