Example, imagine an object Cube in collections 1 and 2 where both
collections are nested to A. Now we set a "color" property as follow:
```
Scene -> GREEN
--
A -> RED
↳ 1 -> BLUE
↳ 2 -> -
```
In this case the object will be RED, because of A↳ 2.
Now if we have:
```
Scene -> GREEN
--
A -> RED
↳ 1 -> -
↳ 2 -> PINK
1 -> -
--
The object will be PINK because of A↳ 2.
Note that the (top level) collection 1 doesn't influence the object color
because there are no overrides on it. The scene render settings (GREEN
in this case) are only used as fallback if an override is not set at
all.
This is to be used from the Outliner, when dragging and dropping
collections from the Active Render Layer
It also includes a cleanup on the outliner so it calls the new
functions. Note: the outliner still needs fix to allow all the
functionality here exposed.
But this will be tackled by Julian Eisel later.
This was causing blender to segfault.
We now add create a new collection and link to the layer before adding
the new object
(also included unittests, and requires updated lib/tests)
Some tests may break Blender, which makes the entire unittest routine to fail.
They are now I isolate the tests into individual files
Kudos to Sybren Stüvel and Sergey Sharybin for the advice.
Note: at the moment test_link.py is failing (since a41bbfb7)
