Set some metadata for images created with GLLara.

This fixes #31. My hope is that I can use this to gauge more accurately what images were created with GLLara.
Support for most of AppleScript, including automated tests.

This also needs to be added for exporting items and rendering images, but in particular for the former, I first want to get to a unified model for this (#65), so I'll do that only then.
Added properties that were mentioned in the scripting definition file but not actually present.

They just mirror the camera, since these are in the model aspects of the camera, but for a user, they'll look more like parts of the window.
Added support for new shader with diffuse and color.

Color has to be set via UI; defaults to white. I'm thinking about allowing this for all shaders. Additional infrastructure was necessary to have default colors and test them properly. Also, I discovered a compile error in the OBJ shaders, which makes me think that I should add an automatic test for them.
Added automated tests for rendering of OBJ files.

This fixes #15 again; the previous commit only solved this for .mesh and .mesh.ascii files.
Started unified exporting interface (#65)

This code will alter the basic composition of exporting significantly. To do this, it will also need extensive tests, which aren't written yet.
model must not be nil.
Fixed a (copied and pasted) typo.