Use sync instead of copy on the explodeWar task

[int128]

This pull request improves processing time and battery consumption for the explodeWar task by using sync task. Current implementation always copies all files (big JARs!) but this copies only modified files.

[loosebazooka]

Interesting idea, we do like to clean the exploded app directory though. Does sync remove files in the destination that are NOT in the source?

[int128]

Yes, sync task removes files not in the source. For example, build/exploded-app/WEB-INF/classes/foo will be removed unless src/main/resources/foo exists.

This task is like the Copy task, except the destination directory will only contain the files copied. All files that exist in the destination directory will be deleted before copying files, unless a Sync.preserve(org.gradle.api.Action) is specified.

https://docs.gradle.org/current/dsl/org.gradle.api.tasks.Sync.html

[loosebazooka]

Thanks @int128 for helping improve the codebase. I'll merge this in.