Differentiate nodes in lineage graph based on namespace

[wslulciuc]

Marquez currently keeps track of data lineage metadata across namespaces. Let's add support in the web UI to color nodes based on namespace to help with troubleshooting upstream and downstream job failures. For example:

In the figure above, we have three namespaces: foo-namespace, bar-namespace, baz-namespace. Each node in the lineage graph is colored based on the namespace they are associated with.

/cc @phixMe