DOC: Better explanation of rcParams "patch.edgecolor" and "patch

.force_edgecolor"

Author: timhoffm

lib/matplotlib/mpl-data/matplotlibrc

@@ -148,8 +148,12 @@
 ## for more information on patch properties.
 #patch.linewidth:       1.0    # edge width in points.
 #patch.facecolor:       C0
-#patch.edgecolor:       black  # if forced, or patch is not filled
-#patch.force_edgecolor: False  # True to always use edgecolor
+#patch.edgecolor:       black  # By default, Patches and Collections do not draw edges.
+                               # This value is only used if facecolor is "none"
+                               # (an Artist without facecolor and edgecolor would be
+                               # invisible)  or if patch.force_edgecolor is True.
+#patch.force_edgecolor: False  # Use patch.edgecolor as the default edgecolor.
+                               # This is mainly relevant for styles.
 #patch.antialiased:     True   # render patches in antialiased (no jaggies)