Add "welcome" page component for unauthenticated users.  Update styles.

* Set min-width for body to 1000px.
* Make style class names more meaningful.
* Make main dayframe html components ("working area" and "widget panel")
  floating.
* Add the "demo" class to the angular app container element
  (selector="[ng-app]").  Currently this only changes whether or not the widget
  panel is fixed position.
* Add "welcome" content to page when user is not authenticated.