Updates to Help Widget and Sidebar Pane

1. Make the Help Widget an optional `floating` or `titlePane` widget.

2. Change `toggleSideBar` function to `togglePane` making it more generic to accommodate additional Content Panes in the future (example is attribute list located below the map).

3. Allow the application to start with the sidebar closed (collapsed).
@tmcgee We need to have the side bar stored in a dom node when not visible or you get errors with the TOC widget.