We need more sophisticated resolution of URIs

[martindholmes]

With @HelenaSabel and @sydb, we decided that we need a function which is passed an attribute which is known to contain one or more pointers, and would resolve all those pointers to URIs, and retrieve and return all the target items from all the pointers as a sequence. The required context can be derived directly from the attribute's context.

[martindholmes]

Starting on this in branch issue-41-retrieval.

[sydb]

If it is to return nodes, though, it should be a template, not a function, eh? (Which is a nice division of labor: a function to read in the values of a pointing attribute and convert them to a sequence of fully-functional pointers, and a template which (using that function) reads in the values of a pointing attribute and returns a sequence of nodes.)