Loader now adds a layer instead of opening a file in Photoshop

This branch implements the Add To Layer action for the loader. It supports both images and PSDs.
The 3 main tasks were:
- Renaming the Open File action to Add To Layer.
- Adding a check to make sure there is a current document.
- Using the Place action to create the layer.
Yeah, you should give the script listener plugin a try. It's scarry what it generates and theres a lot of undocumented parameters. When doing a Google search for these parameters you end up with other people who pretty much do what I did here without even mentionning why they are doing it. I figured I'd at least be honest about it. :)

As for refactoring, you are right, it would be nice. We'd have to refactor and word it very carefully however. Add as a Layer can mean so many things. Do you link or import the data into your PSD? If you import it, what do you do? Do you rasterize it and add a single layer or add as is? And so on.