Moved Data folder into build directory

I had initially placed the data directory in the project root
folder.  It should actually go into the build directory, where
the program gets compiled and run from.
Working version of WaveEqn

The first rev of the WaveEqn program is completed and
commented.  The program computes the wave equation on a fixed
mesh over 5 seconds, with a step size of 1/64 second.

Future improvements could include adaptivly changing the mesh
based on the requirements of the solution, and making it
easier to change the time step, total time, and resolution.