"Beta" flag for unstable/confusing features

[linusha]

We know of some features which are half-baked, but nevertheless sometimes useful (such as the minimap) and also we have some things that are confusing (such as the morph menus), but require larger amounts of thought and work to get right.

I propose the implementation of a "beta" or "advancedUser" flag, that will allow usage of these things and, when not set, will hide the corresponding UI elements as well. This way, we can make the UI easier to get into for newer users (as lively.next can be "a bit much" in the beginning in any way).

This flag should be stored in the browsers local storage or in the localconfig and it might be handy to toggle this via the dashboard, similar to the fastload/slowload toggle.