Drag and drop s-table header using DnD class (Novik#2855)

* Drag and drop s-table header using DnD class

- Modify `DnD` class initialization method a bit, so that the object
  can be attached to an HTML element or an `id` identifier. This is
  a preparation for the following change.
- Merge header cell resizing and moving methods into one object,
  reusing ruTorrent's `DnD` utility class, and thus removes the
  `dxSTable.ColumnMove` object defined in the s-table module that
  did the same thing as the `DnD` class.
- Rearrange header row drag-and-drop event handling process. Resizing,
  moving, and sorting actions are distributed according to the position
  of mouse clicks and displacement of the mouse cursor.
- Remove obsolete properties from S-Table class (`dxSTable.cancelMove`
  and `dxSTable.cancelSort`).

* Use ternary operator for DnD init

js/objects.js

@@ -5,8 +5,16 @@
 
 // Drag & Drop object 
 class DnD {
-	constructor(id, options) {
-		this.obj = $('#' + id);
+	/**
+	 * Construct a drag-and-drop instance.
+	 * @param {string | HTMLElement} dndObj Reference to the drag-and-drop element.
+	 * Can be the HTML `id` of the element, or a reference to the HTML element.
+	 * @param {Object} options Drag and drop options to be passed.
+	 */
+	constructor(dndObj, options) {
+		this.obj = ($type(dndObj) === "string")
+			? $('#' + dndObj)
+			: $(dndObj);
 		const headers = this.obj.find(".dlg-header");
 		const header = headers.length > 0 ? $(headers[0]) : this.obj;
 		this.options = options || {};