* Fixed a bug in the coarse grid density correction that lead to a shift in the correction in some rare cases
* Fixed a bug in restricting fine grid noise when the double size fine grid (for FFT) is actually larger than the domain.
* Added new log file routines that use printf syntax
* Added log file output to most parts of the code
* Removed the stats file output, it is now appended to the log file
New conservative transfer function scheme.
New random number generator that preserves coarse Fourier modes instead of applying Hoffman-Ribak
Some minor bugs fixed.
* Moved hybrid poisson solver from convolution_kernel.cc to poisson.cc
* Fine-tuned deconvolution schemes for various running modes
* Added lots of doxygen documentation
* The DM transfer function is now deconvolved with the cell assignment
function in order to restore power near the Nyquist wavenumber.
* Added an option to change the random number sample cube size
[random]/cubesize. This should be set >128 to generate un-
correlated numbers. True fix pending.
* Removed some unused code
* Increased Buffer size for Gadget-2 output plug-in
