Support custom rulesets and reporters on Java 9+

[jacquerie]

Closes #259
Supersedes and closes #495

Abandons completely the approach of #351 in favor of a simpler idea proposed by @Tapchicoma.

Tested by first building the ktlint-ruleset-template.jar and then running

$ ./gradlew ktlint --args="--ruleset ~/Code/ktlint/ktlint-ruleset-template/build/libs/ktlint-ruleset-template.jar ~/Code/ktlint/ktlint/src/**/*.kt"

[Tapchicoma]

I see following warning, when running on OpenJDK 11.0.4:

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by com.pinterest.ktlint.KtlintCommandLine (file:/command/ktlint/build/run/ktlint) to method java.net.URLClassLoader.addURL(java.net.URL)
WARNING: Please consider reporting this to the maintainers of com.pinterest.ktlint.KtlintCommandLine
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

Another thing, I've noticed, is with this approach custom ruleset violations are not failing the build 😞

[Tapchicoma]

I think, I found a solution. Will open a PR soon.

[shashachu]

sorry for the delay- i just merged in @Tapchicoma 's PR - will this unblock you?

[jacquerie]

sorry for the delay- i just merged in @Tapchicoma 's PR - will this unblock you?

Great, thanks! Well, the last step would be to get a 0.35.0 release containing this fix... but I guess I just need to wait for it to happen.

[shashachu]

sorry for the delay- i just merged in @Tapchicoma 's PR - will this unblock you?

Great, thanks! Well, the last step would be to get a 0.35.0 release containing this fix... but I guess I just need to wait for it to happen.

If you like, you should be able to use a snapshot version of ktlint (see the README) to verify that it works until we release 0.35.0. There are a couple bugs I'd like to squash before our next release.

[jacquerie]

If you like, you should be able to use a snapshot version of ktlint (see the README) to verify that it works until we release 0.35.0.

I'd love to, but we use ktlint through ktlint-gradle, so I ran into the issue that this PR will fix: JLLeitschuh/ktlint-gradle#281. So I'll still have to wait, either for a new version of ktlint or a new version of ktlint-gradle !