This commit does six things
* changes the animation for the splash screen. To a more subtle animation.
* defers displaying the splash by 1.5 seconds
* defers displaying the splash "loading" text by 2.5 seconds
* defers removing the splash until all Discourse initializers have run
* fixes a display issue in Firefox
* Inlines the SVG as a base64 and inlines the required CSS.
The encoded SVG is hard coded for now, but we will use a helper to generate that based on the file after some testing.
