Add about dialog to editor component
Merge pull request #465 from kossebau/addEditorAboutDialog

Add about dialog to editor component
Add getElementsByTagName to DomUtils.
Remove dangerous <script/> and <style/> tags before inserting XML into the dom.
<script/> tags are executed when inserted into the DOM. This is unwanted, so they are are removed before the XML is inserted into the DOM.
In addition, <style/> elements can be used to execute code, so they are removed too.