Manage dependencies for kotlin-stdlib-jdk7/8

[sdeleuze]

As explained in the "Split package compatibility" section of
https://blog.jetbrains.com/kotlin/2017/09/kotlin-1-2-beta-is-out/,
kotlin-stdlib-jdk7 and kotlin-stdlib-jdk8 are the recommended
dependencies to use with Kotlin 1.2 for Java 9+ compatibility.

[snicoll]

which replace the old kotlin-stdlib-jre7 and kotlin-stdlib-jre8.

Should we remove those then?

[sdeleuze]

No because kotlin-stdlib-jre7 and kotlin-stdlib-jre8 can still be used by some projects (these upgrading Kotlin version from 1.1 for example), so I think we should define their version as long as the Kotlin version we use publish such artifacts.