Java 11?

[Jolanrensen]

The DataFrame library currently targets Java 8. This is to ensure the widest compatibility across the board and follow Kotlin/JVM itself.
However, kotlin-jupyter, a key component for DataFrame, recently updated to Java 11, making it impossible to update it.

We have two options:

1. Update to Java 11
2. Extract Jupyter dependencies to different module #241
3. (Convince @ileasile to downgrade again)

What should we do?

[ileasile]

BTW, kandy uses 11 for a year already
Kotlin/kandy@1f5d01e

[Jolanrensen]

https://youtrack.jetbrains.com/issue/KTNB-686

[Jolanrensen]

Can be solved by solving #241. Then we can keep Java 8 but update Jupyter to 11