Add onload events for proper loading (if it's the reason of some problems)

[ErniW]

There is a problem while loading fonts (in loader), it's possibly due to fact that the order of loading should be different.

Adding this to both index and app will make sure that everything loads properly.

This issue rarely occurs with the layout itself.

Probably the "Invalid UUID" error is caused by same reason.

[ErniW]

I don't know how to test it with any measurements. Maybe just changing in index.html order of loaded assets (involt.js and iframe) will do what I want. Maybe I need to check with heavy content inside app.