Improve the 'filter()' function by using FFT
removed the direct calls to the seperate convolution functions and some code that will not be needed without the direct calls. relates to ticket #765.
added the version of the matrix filter that uses the fast fourier transformation for faster calculation for large kernel matrices as described in #765. for now all three methods exist side by side an can be selected by the user.
Main window can not be opened while having plots in full screen
Main window can not be opened while having plots in full screen
added a minor name fix for the random distributions from ticket #759. changed the doxyfile to relative paths for better portability.
Add more random number distributions
added the documentation for the number distribution functions as described in ticket #759