Starting work on flexible metadata scanning api.
switch to latest galley snapshot version, and started fleshing out a quick POM expression/xpath resolver.
Adjust to new batching api and virt vs concrete resources. I'm still planning to implement caching and batching of non-retrieval operations like existence and listing, but this is a start.
merging metadata-scanner branch with some incomplete features for scanning/attaching arbitrary metadata to the depgraph nodes.
starting work on a patching api for fixing up relationships after discovery, to compensate for projects like distribution projects that don't do a good job accounting for their dependencies in a way that can be graphed easily.