Gradle 4.4 support

[kyegupov]

Internal APIs have changed for UsageContext and Usage, so quite a bunch of changes were needed to adapt to that.

[palantirtech]

Thanks for your interest in palantir/gradle-docker, @kyegupov! Before we can accept your pull request, you need to sign our contributor license agreement - just visit https://cla.palantir.com/ and follow the instructions. Once you sign, I'll automatically update this pull request.

[uschi2000]

I'm fine with this. The alternative would to remove the support for docker dependencies, not sure anyone uses this? @jared2501 @gracew

[jared2501]

No where ended up taking the docker dependencies stuff as far as I know

[gracew]

I think we use docker dependencies incorrectly in a bunch of places. I'm fine with either merging this or deleting DockerComponent.

[billbindi]

I can tell you that we do in fact use this and I would appreciate this remaining, but just upgrading (i.e. merging this pr) for the newer gradle APIs.

[uschi2000]

OK, too bad.

[uschi2000]

thanks @kyegupov

[billbindi]

@uschi2000 it looks like this has had some troubles publishing. Judging by the gradle plugin page (https://plugins.gradle.org/plugin/com.palantir.docker) it hasn't published since 0.13.0. This most recent one looks like a test failure, which is odd since the pr passed that test just fine. Any chance you could try a retrigger to see if it is just a flickering test?

[uschi2000]

Working on it.

[uschi2000]

0.17.0 is now on bintray. docker plugin portal publishing is still broken.