[Bf-python] Script link additions

[Willian Padovani Germano]

Hi,

Been busy this week (sorry JMS and Campbell, had no time to work on 
updating scripts and checking patches yet) with a few additions 
committed today that need a little explaining:

The "Render" script link (slink for short) was added.  *It runs twice*, 
before and after rendering.  Before rendering Blender.event is "Render" 
and after, "PostRender".  This was done so render slinks can clean up 
whatever data they created solely for rendering.

So suggested is that "Render" slinks do something like this (not 
mentioning the case of script being run with ALT+P as a normal script):

import Blender

if Blender.event == "Render":
  # prepare for rendering...
elif Blender.event == "PostRender":
  # clean up, revert changes if needed...

I disabled "FrameChanged" during renders, since there's a render event 
now.  To standardize things it's better to use FrameChanged only for 
what it says: frame changes.  It's still used in Scene changes, too, not 
sure if it should go away there and be substituted by "OnLoad".

All slinks can also be disabled now via "blender -y" or the new button 
at the script buttons tab.  Adding slinks has also changed (improved?) a 
bit, just try to see.

The other addition is called "space handlers", but I'll put it in 
another email, this one is big enough.

-- 
Willian