Make check mark green if non-leaf QC item has no children.

If a test passes for all items, show the (single) check mark
and colour it green.

Leaf nodes always have their check mark in the default colour.

Related to #90.

lib/www/client/source/src/views/QC.vue

@@ -117,7 +117,7 @@
                     color="primary"
                     title="Accept this value"
                     @click="accept(item)">
-                    <v-icon small>mdi-check</v-icon>
+                    <v-icon small :color="(item.children && item.children.length == 0)? 'green':''">mdi-check</v-icon>
                   </v-btn>
                 </v-hover>
               </template>