Add extension functions to convert Array to persistent collections

[SageDroid]

The plus and minus extension functions for PersistentCollection, PersistentList and PersistentSet support Array as argument but there are no extension functions to convert an array to persistent collections.

Example for converting an Array to a PersistentList:
fun <T> Array<out T>.toPersistentList(): PersistentList<T> = persistentListOf<T>() + this