~ Improved to support multi references
~ Improved to support multi references
~ Improved to support multi references
~ Improved to support multi references
~ Improved to support multi references
~ Improved to support multi references
~ Improved to support multi references
~ Super supported and do not try to lengthen extension function calls in any situation
~ test for extension property
++ ~ test for extension property
~ prettification
Refactor: rewrite JetReferenceContributor to kotlin

Add additional utilities to track what psi elements are capable of holding references
++ somewhere; AbstractPolyVariantJetReference.java removed
Refactor: move utilities to a separate file
~ prettification