bsdgrep(1): Fix coloring to respect --color=when properly

[kevans]

Summary

bsdgrep(1) does not currently respect --color=when, specifically for when=auto. It currently either always colors or it never colors. If --color=auto, don't color fulltext matches, just partial line matches, and if the -o flag is set we generally shouldn't color unless --color=always

Test Plan

Run kyua tests to make sure we've introduced no regressions.

[kevans]

Remove bogus symlink that snuck in

[kevans]

Apologies for the noise -- too tired for this. =)