Initial version of exposure corrected image
Update to c++0x
Optimizations
Add .gitignore
Copy header
Move exposure_smooth to new intelligent algorithm
(factors of several 10s faster typically)
Minor comments
changes to exposure_smooth
Revert to old algorithm. Problem is that the S/N does not increase properly with radius if background is present, so this algorithm can break. Use accumulate_smooth_expcorr for case with no background.