Fixed normal modes code:

* Use FFT wrapper, rather than platform libraries for normal modes.
* Clean up unused variables.
* Some readability and style changes.
Style, readability, unused variables, if-else structure.
Put serial debug code back in.
Put example of parallel debug code back in.
Reorder as in implementations.
Merge pull request #10 from OndrejMarsalek/normal-modes

Fixed normal modes transformation