release 0.5.0:
Libgpiv has undergone a Kafka revision: The API has been reduced, symplified and changed 
drasticly. Structures for containing PIV and other data have been extended with comments 
and 3-dimensional use (for future extensions), a new structure for containing the image 
frame(s) and header has been created. Fftw version 3 is used for FT and correlation. 
The keys for parameters in the gpiv.conf have been changed and uniformed. All gpiv_eval* 
have been changed to gpiv_piv*.
