Support storing multiple graphs per file

[daniel-j-h]

At the moment the spec stores a single graph which might contain disconnected components. We should support the use case where we want to store many mid-size to small graphs in the same file, so that we don't need to create one file per graph.

To implement multiple graphs in the spec, maybe it's good enough to have a new uint tag per graph entity that tells us which graph this data is associated with.

e.g.

GraphChunk
  graphId = 4
  offsets = [..]
  targets = [..]

this graph chunk is for the graph with id 4; something like this?

Related

• Come up with a strategy for graph, node, edge properties #4