Remove unused attributes from parent elements

unittests/move-common-attributes-to-grandparent.svg

@@ -0,0 +1,10 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg xmlns="http://www.w3.org/2000/svg">
+<g id="grampa" fill-opacity="0.4">
+  <g stroke-opacity="0.8">
+    <rect fill="#0F0" stroke="#0F0" stroke-width="5" width="100" height="300"/>
+    <rect fill="#0F0" width="200" height="100" />
+  </g>
+  <circle fill="#0F0" stroke="0F0" cx="50" cy="50" r="20" />
+</g>
+</svg>

unittests/remove-unused-attributes-on-parent.svg

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8" standalone="no"?>
+<svg xmlns="http://www.w3.org/2000/svg">
+ <g fill="#0F0" stroke="#000">
+  <rect stroke="#0F0" stroke-width="5" width="100" height="300"/>
+  <rect fill="#FFF" stroke="#000" width="200" height="100"/>
+  <circle fill="#0F0" stroke="#0F0" cx="50" cy="50" r="20"/>
+ </g>
+</svg>

unittests/scour-lengths.svg

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8" standalone="no"?>
-<svg xmlns="http://www.w3.org/2000/svg">
+<svg xmlns="http://www.w3.org/2000/svg" x="1.0000000" y="1.0000000">
 	<rect x="123.4567" y="123.00" width="300.00001" height="1E+02" fill="lime" />
 	<rect x="123.4567px" y="35.000ex" width="300.00001pt" height="5E+01%" fill="blue" />
 </svg>