Consider changing name of compare command

[crimsleap]

'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).

[snibgo]

IM has changed all the names. There is now one name: "magick". Eg "magick identify" and "magick compare".

Depending on how you install, the old names are there for backwards compatibility. But new work that is written for v7 should generally not use the old names.