Material: Mateiral editor UI fixes

- Fixed color buttons
- Introduced "Section Color" property
- Fixed named properties
- Added preview icons
- Remember UI dimensions and expanded states

src/Mod/Material/materialtools/cardutils.py

@@ -99,11 +99,12 @@ def get_material_resources(category='Solid'):
         custom_mat_dir = mat_prefs.GetString("CustomMaterialsDir", "")
         if os.path.exists(custom_mat_dir):
             resources[custom_mat_dir] = ":/icons/user.svg"
-        else:
-            FreeCAD.Console.PrintError(
-                'Custom material directory set by user: {} does not exist.\n'
-                .format(custom_mat_dir)
-            )
+        # fail silently
+        #else:
+        #    FreeCAD.Console.PrintError(
+        #        'Custom material directory set by user: {} does not exist.\n'
+        #        .format(custom_mat_dir)
+        #    )
 
     return resources
 
@@ -229,14 +230,18 @@ def get_material_template(withSpaces=False):
         # on attributes, add a space before a capital letter
         # will be used for better display in the ui
         import re
+        new_template = []
         for group in template_data:
+            new_group = {}
             gg = list(group.keys())[0]  # group dict has only one key
             # iterating over a dict and changing it is not allowed
             # thus it is iterated over a list of the keys
+            new_group[gg] = {}
             for proper in list(group[gg].keys()):
                 new_proper = re.sub(r"(\w)([A-Z]+)", r"\1 \2", proper)
-                group[gg][new_proper] = group[gg][proper]
-                del group[gg][proper]
+                new_group[gg][new_proper] = group[gg][proper]
+            new_template.append(new_group)
+        template_data = new_template
     return template_data