Add ability to whitelist auto instruments for non-controller classes

[J-Swift]

There is a way to blacklist files for auto instruments, but no way to whitelist non-controller classes. My use-case is that I'm working on a rails app that heavily utilizes Concerns. Since those are not 'controller classes' I don't get insight into some hot-spots. It would be nice to be able to specify these classes so that they can also be instrumented.

[ioquatix]

This makes sense.

I guess we should allow users to specify more than just controller classes.

[m9]

i second this, i have pretty same issue as @J-Swift do, and would be happy to get concerns(and other non-controller classes) instrumented.