Consolidate skip behavior (take two)

[jherico]

See #969 for the first version of this fix

This is a second attempt that preserves the distinction between spotless.apply.skip and spotless.check.skip

[nedtwigg]

Looks like it needs a spotless:apply :)

[lutovich]

Looks good to me. Added one tiny comment. Thanks for the fix!

[nedtwigg]

Thanks to you both for your patience with me :) Let me know if you'd like it to get released now, but I assume it's okay to wait for some other features to pile on to the release train first.

[jherico]

@nedtwigg compared to trying to get traction on the bugs and PRs I've opened against Elasticsearch and Flink this all happened at lightning speed so thanks, one less thing I have to keep track of.