Contrast adjusting not like IJ1

[ctrueden]

In the imagej devel maling list Gabriel Landini noted the following issues with the Brightness/Contrast plugin:

Compare Contrast in IJ1 with IJ2. In IJ2 the contrast does not respect the brightness, as (without any brightness tweaking) the contrast should narrow the LUT to 127 or so. Currently IJ2 at 100 setting of contrast has a minimum of 0 and a maximum of 4.67 (?). I think contrast should control the width of the LUT from both sides, while keeping it centred. Currently it affects the max value and as a consequence it changes both the width and the position of the lut. So "Contrast" behaves same the "Maximum" slider of IJ1.

Migrated-From: http://trac.imagej.net/ticket/1802