Make Silex load faster

This is a relatively easy task for a programmer to start with Silex

Use dynamic imports of webpack to load the app progressively:

• first the App.ts
• then rest of Silex code
• also split the third party modules such as Monaco editor, wysihtml editor, prodotype, cloud explorer, ...

I made the direct download badge. The icon is get_app from https://github.com/google/material-design-icons, used under Apache v2. This is compatible with distributing the badge under GPLv3+ like the rest of the project, but still requires attribution, which we don't currently have. I believe Apache v2 also requires us to distribute the full text of the license. So, to do:

• Add a note tha