Bring back support for paper.setup('id') again, and document it properly.

Closes #510.

src/core/PaperScope.js

@@ -182,8 +182,9 @@ var PaperScope = Base.extend(/** @lends PaperScope# */{
      * Sets up an empty project for us. If a canvas is provided, it also creates
      * a {@link View} for it, both linked to this scope.
      *
-     * @param {HTMLCanvasElement} element the HTML canvas this scope should be
+     * @param {HTMLCanvasElement|String} element the HTML canvas element this
-     * associated with.
+     * scope should be associated with, or an ID string by which to find the
+     * element.
      */
     setup: function(element) {
         // Make sure this is the active scope, so the created project and view

src/item/Raster.js

@@ -37,9 +37,10 @@ var Raster = Item.extend(/** @lends Raster# */{
      * string describing the URL to load the image from, or the ID of a DOM
      * element to get the image from (either a DOM Image or a Canvas).
      *
-     * @param {HTMLImageElement|Canvas|String} [source] the source of the raster
+     * @param {HTMLImageElement|HTMLCanvasElement|String} [source] the source of
+     * the raster
      * @param {Point} [position] the center position at which the raster item is
-     * placed.
+     * placed
      *
      * @example {@paperscript height=300} // Creating a raster using a url
      * var url = 'http://upload.wikimedia.org/wikipedia/en/2/24/Lenna.png';
@@ -285,7 +286,7 @@ var Raster = Item.extend(/** @lends Raster# */{
      * a data-url.
      *
      * @bean
-     * @type HTMLImageElement|Canvas|String
+     * @type HTMLImageElement|HTMLCanvasElement|String
      *
      * @example {@paperscript}
      * var raster = new Raster();

src/project/Project.js

@@ -43,8 +43,9 @@ var Project = PaperScopeItem.extend(/** @lends Project# */{
      * Note that when working with PaperScript, a project is automatically
      * created for us and the {@link PaperScope#project} variable points to it.
      *
-     * @param {HTMLCanvasElement} element the HTML canvas element that should be
+     * @param {HTMLCanvasElement|String} element the HTML canvas element that
-     * used as the element for the view.
+     * should be used as the element for the view, or an ID string by which to
+     * find the element.
      */
     initialize: function Project(element) {
         // Activate straight away by passing true to PaperScopeItem constructor,

src/ui/View.js

@@ -669,6 +669,10 @@ var View = Base.extend(Callback, /** @lends View# */{
         _id: 0,
 
         create: function(project, element) {
+/*#*/ if (__options.environment == 'browser') {
+            if (typeof element === 'string')
+                element = document.getElementById(element);
+/*#*/ } // __options.environment == 'browser'
             // Factory to provide the right View subclass for a given element.
             // Produces only CanvasViews for now:
             return new CanvasView(project, element);