Explicitly block nested updates inside immutable collections fields

[loyada]

Currently it just protects the structure instance with defensive copies, but it will be more developer-friendly if it will explicitly raise an appropriate exception.
For example, if we defined
m = ImmutableArray[Map[String, Integer]]

and we try to change m[0]['xxx'] , then it should throw an appropriate exception.

[loyada]

done in 93e2ad3