About ImageJ: fall back to a signed, 16-bit gradient

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
About ImageJ: remove unnecessary restrictions on the images

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
About ImageJ: shorten the long hex string if possible

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Merge branch 'master' of git://github.com/imagej/imagej
About ImageJ: Actually, fall back to an 8-bit gradient

... because we cannot yet handle more than 8-bit in color merges.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
About ImageJ: do not *require* an 8-bit RGB image

If the image used for the 'About ImageJ' command is not an RGB image,
no big deal. We can display more than just that kind of images.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
DefaultLUTService: remove redundant null check
LUTService: remove obsolete comment