jhatwich/layer comps+size

To use this feature add a layer comp and name it something like "overview.png" or "200% overview.png"
I'm cleaning this code up and adding a few comments to hopefully make it clearer.  Sorry about "easyScale" that was part of the hackery I was using to drive scale using convert.exe.

In general the change to _getData is to allow it to render either a layer or layer comp depending on the component passed.