Autocompletion for topic_edit text box

There is now "tab" autocompletion in the topic_edit text box. When you press tab it will try and autocomplete the word. If there is only one suggestion it will complete that word and add a slash at the end. If there is more than one suggestion, it will complete up to where the suggestions diverge.

It also sets the focus to the topic_edit text box when the widget is loaded, so you can start typing immediately.