enh: allow node specific configuration to override master config

Author: satra

examples/fmri_spm.py

@@ -223,6 +223,8 @@ def subjectinfo(subject_id):
 
 contrastestimate = pe.Node(interface = spm.EstimateContrast(), name="contrastestimate")
 contrastestimate.inputs.contrasts = contrasts
+contrastestimate.overwrite = True
+contrastestimate.config = {'execution': {'remove_unnecessary_outputs': False}}
 
 """
 Setup the pipeline

nipype/pipeline/engine.py

@@ -657,7 +657,7 @@ def run(self, plugin=None, plugin_args=None, updatehash=False):
         self._set_needed_outputs(flatgraph)
         execgraph = generate_expanded_graph(deepcopy(flatgraph))
         for index, node in enumerate(execgraph.nodes()):
-            node.config = self.config
+            node.config = merge_dict(deepcopy(self.config), node.config)
             node.base_dir = self.base_dir
             node.index = index
             if isinstance(node, MapNode):