Rename CIFAR class name, args name

[hatappi]

TODO

• [x] Rename class Cifar to CIFAR.
• [x] Rename argument set_type to type.
• [x] possible to obtain coarse label when CIFAR-100
• [x] fix of test by rename.

[hatappi]

@kou Please review my PullRequest.

[hatappi]

@kou Thank you for review. I fixed. The code became longer than before, but I feel it has become easier to see.

[kou]

Great!