New: columns and cell index() API methods

- The row()/rows() methods have index methods, so it makes sense that
  the column(s) and cell(s) methods also have index methods to get the
  raw information out of the table. Rather than shying away from the
  indexes in 1.10, as has been done with the pervious versions of
  DataTables, 1.10 will embrase them as first class citizens.

- New methods:
  - columns().index()
  - column().index()
  - cells().index()
  - cell().index()

media/src/api/api.cells.js

@@ -67,6 +67,17 @@ _api.register( 'cells().data()', function () {
 } );
 
 
+_api.registerPlural( 'cells().index()', 'cell().index()', function () {
+	return this.iterator( 'cell', function ( settings, row, column ) {
+		return {
+			row: row,
+			column: column,
+			columnVisible: _fnColumnIndexToVisible( settings, column )
+		};
+	} );
+} );
+
+
 _api.register( [
 	'cells().invalidate()',
 	'cell().invalidate()'

media/src/api/api.columns.js

@@ -117,6 +117,16 @@ _api.registerPlural( 'columns().visible()', 'column().visible()', function ( vis
 } );
 
 
+
+_api.registerPlural( 'columns().index()', 'column().index()', function ( type ) {
+	return this.iterator( 'column', function ( settings, column ) {
+		return type === 'visible' ?
+			_fnColumnIndexToVisible( settings, column ) :
+			column;
+	} );
+} );
+
+
 // _api.register( 'columns().show()', function () {
 // 	var selector = this.selector;
 // 	return this.columns( selector.cols, selector.opts ).visible( true );