Support background colour and selection style on ASCellNodes.

Most UITableViewCell properties aren't useful in conjunction with
ASCellNode -- the system's UIView properties are unsupported for
performance reasons, and properties that configure them (e.g., content
indentation) don't affect custom node hierarchies.  This patch adds
support to _ASTableViewCell for the properties that *are* useful.

r=scottg

AsyncDisplayKit/Details/ASRangeController.h

@@ -50,6 +50,15 @@ typedef struct {
 - (NSInteger)numberOfSizedSections;
 - (NSInteger)numberOfSizedRowsInSection:(NSInteger)section;
 
+/**
+ * Configure the specified UITableViewCell's content view, and apply properties from ASCellNode.
+ *
+ * @param cell UITableViewCell to configure.
+ *
+ * @param indexPath Index path for the node of interest.
+ */
+- (void)configureTableViewCell:(UITableViewCell *)cell forIndexPath:(NSIndexPath *)indexPath;
+
 /**
  * Add the sized node for `indexPath` as a subview of `contentView`.
  *