** uses two parameters - value and exponent. the image will be scaled by value*10^exponent
* changed upper limit of Reinhard pre scale to 20
* added histogram display. doesn't seem to work for linear tonemapping for some reason.
* added three noise reduction filters, median, chiu and arneoog's.
* added processing progress feedback to the status bar.
* added a few extra checks to prevent a new processing thread starting before the running one has finished.
* managed to double the .exe size = 4mb



