Consider changing name of compare command

[alexbirkett]

'compare' is a very generic name and it conflicts with other commands called 'compare', for example araixs merge's compare command. (I've also suggested that araxis change the name of their compare command).

[glennrp]

You can change it yourself when you configure ImageMagick:

I always use
--program-prefix=q16

Which turns "compare" into "q16compare", "convert" into "q16convert", etc.

Likewise, I use "q8" for Q8 builds, so they can coexist.

[anthony]

I have been wanting to roll the compare function into IMv7 "magick" but it is not straight forward.