Implement Export queries in Haskell

This is a simple query as it has only two fields, however it's the
first query that doesn't have a clear 'base' object and 1:1
correspondence between such objects and the results (groups, nodes and
networks do so).

We keep nodes as the 'base' object, since that's what we want to
filter on for RPC selection, and we have a very simple type as the
runtime type, since we only have one other field. The
'collectLiveData' function is the one that does the expansion from
[node] to [(node, path)], with the help of 'rpcExtractor'.

Also, this patch introduces a slightly different naming structure for
the exported names out of the module, to reduce naming conflicts.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>