Multiple language support

@cscheid's old branch for pluggable languages
@s-u, I could be wrong, but my faint recollection is that this line (and the fact that Carlos produced this PR 3 days before release 1.1) is the only reason we didn't merge feature-langs.  

Does this extension mechanism (load package using `getNamespace` and then pull the `rcloud.language.support` function from the namespace) look reasonable to you?