[PATCH 0 of 2] extension setup in new order (v3)

[Simon Heimberg]

the new init parameter of load is renamed to setuplater. load does not handle 
execute some steps of the setup itself, it calls the setup function. The update 
of the command table moved from dispatch to extensions.setup. This has the 
advantage that the whole extension initialisation is in one place. But an 
import is inside of the setup function because there is an import cycle else.
(Not breakable by demandimport.)
calling extsetup(ui) is now in a separate patch. Detecting if the extension 
supports the ui argument is done without raising wrong exceptions.

Any comments?

Greetings,
Simon