[any] "contained value" vs "contained object"

[lynnboy]

In [optiona] and [variant], "contained value" is the term refer to the object inside, but in [any], in general it uses "contained object", but still use "contained value" at some places.
We should unify the term as "contained value".

[jensmaurer]

Also, [variant] doesn't italics-define "contained value", but should, to make the index consistent.