Make Kotlin theme to be more like java

[turbanoff]

Hello. I use solarized light color scheme. Currently I'm working on project with both languages: java and kotlin. And it's really hard to read code in kotlin after reading java code. It has too many gray symbols, too blue keywords. It would be nice to have kotlin highlighting almost like java: same colors - same meaning.

[jkaving]

I have never used Kotlin myself, so I don't feel particularly suited to fix this. But I think it sounds reasonable that Kotlin should look similar to Java so pull requests for improving this would be very much appreciated.