Add more API docs.

See #343 for discussion around this
change.

src/GeoExt/data/LayerTreeModel.js

@@ -24,6 +24,8 @@
  *   dynamically if the name of the connected layer changes, if any. Read only.
  * * **component** Ext.Component: The component to be rendered with this node,
  *   if any.
+ * * **disabled** Boolean: Used to reflect whether the associated layer is
+ *   in range (visible in the current map scale).
  *
  * A typical configuration that makes use of some of these extended sttings
  * could look like this:

src/GeoExt/tree/LayerNode.js

@@ -20,6 +20,24 @@
  *         layer: myLayer
  *     }
  *
+ * When the layer associated with this GeoExt.tree.LayerNode is no longer in
+ * range (invisible due to resolution constraints), the layer will be visually
+ * marked as disabled.
+ *
+ * If you do not want this behaviour, include the following CSS code:
+ *
+ *     .gx-tree-row-disabled span.x-tree-node-text {
+ *         opacity: inherit;
+ *         font-style: inherit;
+ *     }
+ *
+ * If additionally you want to make the nodes checkbox unusable when the node is
+ * disabled, you could use the following CSS-snippet:
+ *
+ *     .gx-tree-row-disabled input {
+ *         visibility: hidden;
+ *     }
+ *
  * See GeoExt.data.LayerTreeModel for more details on GeoExt extensions to the
  * node configuration.
  *

src/GeoExt/tree/View.js

@@ -44,6 +44,9 @@ Ext.define('GeoExt.tree.View', {
         return me.callParent(arguments);
     },
 
+    /**
+     * @inheritdoc
+     */
     getRowClass: function(record, rowIndex, rowParams, store) {
         return record.get('disabled') ? 'gx-tree-row-disabled' : '';
     },