Added a framework for the ImageWriter node and it's bindings. It currently does nothing but it is better than nothing... right?
The image writer can now output images! Still plenty of work to do though... see the todos.
Added more features along with some test cases.
Made suggested changes:
OutputImage is now managed by a shared_ptr.
Flags are fixed.
Merge pull request #227 from goddardl/ImageWriter

Image writer
Removed unnecessary collapsible section in Group UI.
Merge branch 'master' of https://github.com/ImageEngine/gaffer