GSoC disney editor

Move after renderer headers section.

The rule is: from the most specific headers to the most general ones:

1. Interface (i.e. the header file that corresponds to the current source file).
2. UI header file when applicable.
3. appleseed.renderer headers.
4. appleseed.foundation headers.
5. appleseed.main headers.
6. Third-party libs headers such as Qt, OpenEXR, SeExpr...
7. Boost headers.
8. Standard headers.