Better dependencies

This does the following:

* Deprecates `as.list`, in favor of `reactivevalues_to_list`.
* Adds `all.names` option to `reactivevalues_to_list`.
* Sets up dependencies properly, depending on the value of `all.names`.
* Renames internal `.allDeps` to `.valuesDeps`.

It turns out that `names.reactivevalues()` can't be modified take an `all.names` option, because `names.default` is defined as `function(x)` not `function(x, all.names)`. So I left it as-is, where `names` returns all the names.