Added some documentation for the project.

NOTES contains information on generating checksums for Hy-Tek
import/export files HY3 and CL2.

TODO contains notes for future work and items to be addressed.
Set the licensing for the project be GPLv3.
Created the CMake build file.

Since we want to be able to build this on Windows, a cross-platform
build environment is required.
Added the libsdif shared library.
Added the rdsdif utility.

This will read and display the records for an SD3 file.