Implement Dataset Refs

[philipbaileynar]

When business logic refers to data that has a ref attribute, ArcRAVE needs the ability to go find that referenced dataset elsewhere in the project. (QRAVE already does this.)

In python we do it this way:

https://github.com/Riverscapes/QRAVEPlugin/blob/dev/src/classes/project.py#L304-L361

Update:

I had to create a sample test project and business logic to test this

It's in nardata at the path nardata/Matt/RefProject.zip (80 Mb)

Two things to check:

• [ ] regular nodes without ref= still load normally
• [ ] Nodes with ref= get the right lookup and appear in the tree
• [ ] Metadata values show correctly for nodes with ref=

[philipbaileynar]

1. Can nodes have both ref and xpath? If so what takes precedence?
2. Can any node type have ref, or just GIS datasets?
3. Does a business logic node that has an xpathlabel and that refers to a project node with a ref, does the xpathlabel refer to the project node or the referenced node?