Add continuation_indent_size

[Van0SS]

I spent several hours figuring out why Intellij IDEA uses Continuation Indent 4 spaces even if I change size directly in the project settings. Turned out that I had EditorConfig plugin enabled which picks up .editorconfig and override all the project settings. But the problem is that it sets Continuation Indent the same as indent_size, which is completely wrong. To fix it Plugin's authors added custom property continuation_indent_size. This property is supported only by IDEA but should not bring any harm for other IDEs.

[elasticmachine]

Pinging @elastic/es-core-infra

[javanna]

@elastic/es-core-infra thoughts on this one?

[javanna]

ping @elastic/es-core-infra do we want to get this one in? Thoughts?

[danielmitterdorfer]

Thank you very much for taking the time and addressing this. I have tested this in IntelliJ IDEA 2018.3 (Community Edition), Build #IC-183.4284.148 and the bundled EditorConfig plugin and unfortunately this setting seems to be ineffective.

Evidence I am basing my assessment on:

• As of today the referenced issue IDEA-145069 is still marked as "open".
• If I add continuation_indent_size to .editorconfig it is reported as an unknown key.
• If I enable "Parameter descriptions on new line" in the IDE configuration in Editor > Code Style > Java > JavaDoc(which according to the docs "uses indent based on the continuation indent value") and format a Javadoc snippet accordingly, it does not honor the continuation_indent_size I have defined in .editorconfig.

As such I hope you do not mind if we close this PR for the time being as the change is ineffective at the moment. If however, the underlying issue in the IDEA repository is fixed, we can definitely reopen this again.