[Bf-python] ID Properties and python hook scripts

[Joe Eagar]

Hi. I was thinking about ID properties and stuff, and I realized we're 
going to need a way to register trusted scripts.  Some sort of generic 
system that'd work for scripts drawing custom ID properties guis and 
also normal scripts.

Basically, a trusted registered script can do these things:
* It can register a function to call whenever a .blend is loaded (e.g. a 
init/re-init function).
* It can register space handler scripts and scriptlinks, which are in 
their own class that can't be disabled (though I think an option to 
disable the whole trusted script system might be a good idea if people 
want it :) )
* It can register a clean-up function that gets called when a different 
.blend is loaded.

The trusted script system would also be extendable, so for example ID 
properties could use it to handle custom-gui scripts for ID properties 
(and wa-hoo! finally panels will have to be wrapped for this to all 
work! fun!).

My ideas for implementation, is that all trusted scripts are 
prebytecompiled (with some way to get them to recompile themselves, not 
sure how).  The system would store the list of registered trusted 
scripts in a special .B.scripts.

The reasons ID properties custom guis needs this, is that obviously you 
don't want your renderman material settings to disappear whenever you 
disable scriptlinks :)

Joe