Improving application startup flow.

Major improvements to distribution index loading.
Implemented new transitional UI for startup.
If **no** distribution index is loaded on startup, completion of startup will be prevented and the user will be shown a message displaying the issue.
Launch errors are now shown as overlays.
Many more minor fixes and enhancements.

app/assets/js/scripts/overlay.js

@@ -17,6 +17,7 @@ function toggleOverlay(toggleState, dismissable = false, content = 'overlayConte
     }
     if(typeof dismissable === 'string'){
         content = dismissable
+        dismissable = false
     }
     if(toggleState){
         document.getElementById('main').setAttribute('overlay', true)