@labels macro

[bramtayl]

Here's one option for making working with labels easier:

Right now we have for example Graphs.outneighbors(meta_graph::MetaGraph, code::Integer) and outneighbor_labels(meta_graph::MetaGraph, label).

Maybe we could have a general pattern where we add a _labels suffix to a Graphs function to make it work with labels instead of code?

We could then have a @labels macro that attaches the _label suffix to all surface-level Graphs function calls?

[gdalle]

Not bad!
Related: #59