:lipstick: fix valueOf
fix private methods

  - SCSequenceableCollection#flatten
  - SCSequenceableCollection#flat
  - SCSequenceableCollection$flatIf
  - SCArrayedCollection::throwIfImmutable
  - SCDictionary::incrementSize
fix SCObject#_doesNotUnderstand -> SCObject#__attr__
fix namespace accessing
:fire: remove code unused
fix how to define a property

  - use `$.addProperty` instead of directly assignment
fix require
fix tests
:muscle: fix SCScript interface