Refactor the linking functionality for the TinyMCE popup.

Functionality that affects the values in the form better fits in
updateFromEditor function, where we expect the form to be modified.
Redraw should only affect visibility parameters.

Also added a more robust reset code, so we can always expect to get at
least a clean form, and re-added missing "target" checkbox.

javascript/HtmlEditorField.js

@@ -468,7 +468,6 @@ ss.editorWrappers['default'] = ss.editorWrappers.tinyMCE;
 		 * which are toggled through a type dropdown. Variations share fields, so there's only one "title" field in the form.
 		 */
 		$('form.htmleditorfield-linkform').entwine({
-
 			// TODO Entwine doesn't respect submits triggered by ENTER key
 			onsubmit: function(e) {
 				this.insertLink();
@@ -477,36 +476,27 @@ ss.editorWrappers['default'] = ss.editorWrappers.tinyMCE;
 			},
 			resetFields: function() {
 				this._super();
-				this.find('fieldset :input:not(:radio)').val('').change();
+
+				// Reset the form using a native call. This will also correctly reset checkboxes and radio buttons.
+				this[0].reset();
 			},
-			redraw: function(setDefaults) {
+			redraw: function() {
 				this._super();
 
 				var linkType = this.find(':input[name=LinkType]:checked').val(), list = ['internal', 'external', 'file', 'email'];
 
-				// If we haven't selected an existing link, then just make sure we default to "internal" for the link type.
-				if(!linkType) {
-					this.find(':input[name=LinkType]').val(['internal']);
-					linkType = 'internal';
-				}
-
 				this.addAnchorSelector();
 
-				// Toggle field visibility and state based on type selection
+				// Toggle field visibility depending on the link type.
 				this.find('div.content .field').hide();
 				this.find('.field#LinkType').show();
 				this.find('.field#' + linkType).show();
 				if(linkType == 'internal' || linkType == 'anchor') this.find('.field#Anchor').show();
+				if(linkType !== 'email') this.find('.field#TargetBlank').show();
 				if(linkType == 'anchor') {
 					this.find('.field#AnchorSelector').show();
 					this.find('.field#AnchorRefresh').show();
 				}
-
-				this.find(':input[name=TargetBlank]').attr('disabled', (linkType == 'email'));
-
-				if(typeof setDefaults == 'undefined' || setDefaults) {
-					this.find(':input[name=TargetBlank]').attr('checked', (linkType == 'file'));
-				}
 			},
 			insertLink: function() {
 				var href, target = null, anchor = this.find(':input[name=Anchor]').val();
@@ -614,16 +604,24 @@ ss.editorWrappers['default'] = ss.editorWrappers.tinyMCE;
 					selector.append($('<option value="'+anchors[j]+'">'+anchors[j]+'</option>'));
 				}
 			},
+			/**
+			 * Updates the state of the dialog inputs to match the editor selection.
+			 * If selection does not contain a link, resets the fields.
+			 */
 			updateFromEditor: function() {
 				var htmlTagPattern = /<\S[^><]*>/g, fieldName, data = this.getCurrentLink();
-				
+
 				if(data) {
 					for(fieldName in data) {
 						var el = this.find(':input[name=' + fieldName + ']'), selected = data[fieldName];
 						// Remove html tags in the selected text that occurs on IE browsers
 						if(typeof(selected) == 'string') selected = selected.replace(htmlTagPattern, ''); 
-						if(el.is(':radio')) {
-							el.val([selected]).change(); // setting as an arry due to jQuery quirks
+
+						// Set values and invoke the triggers (e.g. for TreeDropdownField).
+						if(el.is(':checkbox')) {
+							el.prop('checked', selected).change();
+						} else if(el.is(':radio')) {
+							el.val([selected]).change();
 						} else {
 							el.val(selected).change();
 						}