Rename CallableDescriptorCollectors.java to CallableDescriptorCollectors.kt
Rewrote CallableDescriptorCollectors to Kotlin
Rename: NO_RECEIVER_ADMITTED -> NO_RECEIVER_ALLOWED
Slightly reduce number of candidates in task prioritizer
  return only extensions (functions) when we expecting extensions (not all functions);
  for properties it's not that easy: they may have extension function types, and we want to avoid early computing of deferred types
  rename: getNonMembersByName -> getExtensionsByName

Report NO_RECEIVER_ALLOWED for '42.(f)()' where f: () -> Unit in TracingStrategyForInvoke
(we don't store candidates for such 'invoke' functions any more)
KT-5854 Incorrect 'Nested class should be qualified'
 #KT-5854 Fixed
KT-5455 Need warning about redundant type cast
 #KT-5455 Fixed
Small refactoring in CandidateResolver
KT-5971 Missing error when fun argument is safe call
 #KT-5971 Fixed
KT-6026 Exception on instantiating a nested class in an anonymous object
 #KT-6026 Fixed
Rename: casted -> cast
Refactoring: inlined 'collectSmartCastReceiverValues'