Split multiple auto-config classes into separate files

[therepanic]

I wanted to do this earlier #226 (comment) but it didn't fit the context of the PR. However, I think we should still make this change. I don't see any reason why we should keep it as it is, since keeping classes in one file is bad practice.

Another trigger was #231. I believe this fix can partially solve the problem; we can refer to the auto configurations and disable them. I can't say for sure how well it solves the problem, so I'm not attaching this issue to this PR.

I also removed the checkstyle tags from the auto configurations (//CHECKSTYLE:OFF/ON) as they are no longer needed. Without them, checkstyle complained that separate classes cannot be stored in one file. Accordingly, checkstyle will now be applied to each class in the files.

[therepanic]

I just saw 866a7ec. However, I don't think that's an obstacle.

[onobc]

👋🏻 @therepanic
Thanks for the proposal. I have assigned myself to review and will get to it asap.

[dsyer]

It's -1 from me really for this change. The whole point of those classes was that they were package private and most likely to be retired/evolved when we integrate with Spring Boot, so we don't want people to be able to get hold of them. You might as well keep them all in the same place at that point IMO - it's neater.

[onobc]

Thanks for taking the time to make the changes @therepanic . However, I agree w/ @dsyer as the

1. We are about to move all auto-configuration into Spring Boot and things will shift during that move.
2. Coarse grained auto-configuration w/ nested configurations is a common pattern in Spring Boot

I'm going to close this one. Again, thank you for all your contributions.