Make material color the same across Block Diagrams (#335)

Originally, the same material would result in a different color in a
diagram for a different block within the same report (For example, Sodium would be
Red in one image, but Yellow in another). This change adds the ability
to pass in a list of all materials that would be within all of these
block diagrams, so that if you were to plot multiple block diagrams that
had the material Sodium, Sodium would always be the same color in each
diagram.

Also, got rid of bbox_to_anchor argument for the pltkwargs of
saveFig since it had the warning "MatplotlibDeprecationWarning:
savefig() got unexpected keyword argument "bbox_to_anchor" which is no
longer supported as of 3.3 and will become an error two minor releases
later", and removing it still allowed for the legend to be centered
at the right hand side of the Diagrams.

armi/utils/plotting.py

@@ -1309,7 +1309,7 @@ def _makeComponentPatch(component, position, cold):
     return [blockPatch]
 
 
-def plotBlockDiagram(block, fName, cold, cmapName="RdYlBu"):
+def plotBlockDiagram(block, fName, cold, cmapName="RdYlBu", materialList=None):
     """Given a Block with a spatial Grid, plot the diagram of
     it with all of its components. (wire, duct, coolant, etc...)
 
@@ -1322,45 +1322,50 @@ def plotBlockDiagram(block, fName, cold, cmapName="RdYlBu"):
         true is for cold temps, hot is false.
     cmapName : String
         name of a colorMap to use for block colors
+    materialList: List
+        a list of material names across all blocks to be plotted
+        so that same material on all diagrams will have the same color.
     """
 
     fig, ax = plt.subplots(figsize=(50, 50), dpi=100)
 
     if block.spatialGrid is None:
         return None
+
+    if materialList is None:
+        materialList = []
+        for component in block:
+            if component.material.name not in materialList:
+                materialList.append(component.material.name)
+
+    materialMap = {
+        material: ai for ai, material in enumerate(numpy.unique(materialList))
+    }
     patches, data, name = _makeBlockPinPatches(block, cold)
 
     collection = matplotlib.collections.PatchCollection(
         patches, cmap=cmapName, alpha=1.0
     )
 
-    b, c = numpy.unique(numpy.array(data), return_inverse=True)
-    colorMap = dict()
-    materialMap = defaultdict(set)
+    allColors = numpy.array(list(materialMap.values()))
+    ourColors = numpy.array([materialMap[materialName] for materialName in data])
 
-    for ai in range(len(c)):
-        colorMap[data[ai]] = c[ai]
-        materialMap[data[ai]].add(name[ai])
-
-    collection.set_array(c)
+    collection.set_array(ourColors)
     ax.add_collection(collection)
-    collection.norm.autoscale(numpy.array(c))
-
-    # We want the map from color ----> component
+    collection.norm.autoscale(allColors)
 
     legendMap = [
         (
-            colorMap[materialName],
+            materialMap[materialName],
             "",
             "{}".format(materialName),
         )
-        for materialName in colorMap
+        for materialName in numpy.unique(data)
     ]
     legend = _createLegend(legendMap, collection, size=90, shape=Rectangle)
     pltKwargs = {
         "bbox_extra_artists": (legend,),
         "bbox_inches": "tight",
-        "bbox_to_anchor": "(0.75, 1.15)",
     }
 
     ax.set_xticks([])