Move instigating source out of contributing paths (#253)

* Refactor contributing_paths into contributing_sources, deleting project node sources

* Instead of changing contributing_paths, add instigating_source

* Remove InstanceMetadata::project_node

* Stop pushing project path to front of contributing_paths since it doesn't matter now

* Remove accidental UI change for path display

src/snapshot_middleware/project.rs

@@ -63,7 +63,7 @@ impl SnapshotMiddleware for SnapshotProject {
         snapshot
             .metadata
             .contributing_paths
-            .insert(0, entry.path().to_path_buf());
+            .push(entry.path().to_path_buf());
 
         Ok(Some(snapshot))
     }