FCI interpolation working in simple cases

Only tested interpolation in Z for now

To plot interpolating function:
o Run "python simple_test.py" to generate the input file
  (simple_test.nc)
o Modify data/BOUT.inp, setting grid to simple_test.nc

o Run fci_slab

o Run "python plot_funcs.py"

This should produce a PDF "plot_funcs.pdf"