Limit of divFree RBF interpolant

Add the file limitOfdivFreeRBF.m, still in construction.
The idea is to use the symbolic toolbox to invert the interpolation matrix
of the divergence-free RBF interpolant analytically.

Later we want to compare this interpolant with the divergence-free
polynomial interpolant.
Updating and adding some files

It is a long time since the last commit. Find some crucial bugs on the
divergence-free kernel matrix and the interpolant form. There is still
bugs which I'm trying to find out. Here is my observations on each file:

Changed files

- FandG.m
  Now outputed functions also depend on the shape parameter $\varepsilon$.

- RBFdivFreeInterp.m
  Updated to work with new FandG.m

- RBF_DivFreeMatrix.m
  Function now outputs an extra output argument, the interpolation matrix
  Aep as anonymous function of the shape parameter.

- FD_DivFreeMatrixStream.m
  Function check for number of outputs to calculate only what is
  necessary, i.e., it saves times when utilize in other functions.

- RBF_DivFreeMatrix.m
  Found some errors in the formula of the kernel matrix and now we are
  using ".'" to take the transpose instead of "'" which is hermitian of a
  matrix.

- RBFdivFreeInterp.m
  Fixed some mistakes in the formula of the divergence-free interpolant.

- limitOfdivFreeRBF.m
  Removed the Tal-Ezer mapping due to some interpolation errors when using
  symbolic toolbox. For now, I'm using only equally-spaced points. I'm
  also making sure all the calculations are symbolic using the sym command
  and converting to double at the end.
  OBSERVATION: This file is producing RBF interpolants that goes to
  infinity, which we are not expecting since we don't get those results in
  the contourPade.m file. We need to recheck this file an files that are
  being used by it to see if there is any problems on them.

New Files

- RBFdivFreeInterpComplex.m
  Calculates the divergence-free interpolant for a matrix or a vector of
  shape parameters (they can be complex numbers) and a given set of
  evaluation points.

- contourPade1D.m
  Calculates the limit of the RBF interpolant when the shape parameter
  goes to 0. For now, it only uses the Cauchy integral formula.

- contourPade.m
  Calculate the limit of the divergence-free interpolant when the shape
  parameter goes to 0. For now, it only yses the Cauchy intergral formula.

- symFlatLimitdivFreeRBF.m
  This was an attempt of looking to the flat limit of the divergence-free
  RBFs. The problem is that I didn't consider the coefficients s_k's to
  depend on the shape parameter, in fact, they are going to infinity and
  the basis functions to zero.

That's it for now. There is still probably some bugs in the code, since
currently the file limitOfdivFreeRBF.m is producing RBF interpolants that
goes to infinity. This might be a problem in this file or any other that
is being used by it.

This is probably one of the largest commits I've wrote, which is not
ideal. I will be more consistent with commits to avoid this issue.
Speed up some scripts

Did some modifications in a couple functions to calculate only what is
necessary, saving computational time in some scripts and functions.

Full list of important changes:

RBF_DivFreeMatrix.m
  - Add the possibility of return or not the differentiation matrices Dx
    and Dy, this speed up certain scripts.
  - Also, the code that generates the interpolation matrices (and the
    derivative matrices) was rewriten for simplicity.

RBFdivFreeInterp.m
  - Change the inputs to avoid recalculating distance and difference
    matrices everytime we want to see the interpolant.

RBFdivFreeInterpComplex.m
  - Function was adapted to work with changed RBFdivFreeInterp.m.

contourPade.m
  - Using changed RBF_DivFreeMatrix.m. Saves time not calculating Dx and
    Dy.
  - Code was adapted to work with changed RBFdivFreeInterpComplex.m.
  - Change the way we reshape the RHS vector for better understanding and
    simplicity.

lebesgueFunctionsRBF.m and limitOfdivFreeRBF.m
  - Code was adapted to work with changed RBF_DivFreeMatrix.m and
    RBFdivFreeInterp.m.
Finding the interpolant exactly

Add some more code to symFlatLimitdivFree.m to calculate the interpolant
analytically. For the 9 point stencil, some of the cardinal functions go
to infinity.
Fixing kernel construction

Was using a wrong formula to construct the kernel.
Comparing symbolic with contour-Padé (flat limit)

Add a new file to compare the symbolic limit with the results from the
contour-Padé on the flat limit, ie, when the shape parameter is zero.

I also fixed the kernel that was used in the function RBFdivFreeInterp.m.
Looking to the limit using chebfun2

Add functions to use chebfun2 with comparingSymAndCP.m script. The idea is
to use the limit from the countour-Padè algorithm (Cauchy integral) and
then use the chebfun2 to get a polynomial approximation.

New files:

chebpoly.m : creates the a symbolic expression for the Chebyshev
             polynomial.

chebpoly2function.m : truncates the chebfun2 approximation and output a
                      anonymous function.
Better output and bug fixes on old code

Displaying the coefficients of the truncated polynomial that we get using
chebfun2.

Also fix a bug on testConvergence Derivative.m
Adding test to convergence for RBF-FD

Testing the convergence of the derivatives for different grids.
Adding new test function

testFunction2 give more divergence-free vector fields to test the accuracy
of the derivatives.