Simplify the automation integration

By requiring/assuming that all test PSDs have asset generation disabled. Requires commit [1e7c5cba79](https://github.com/adobe-photoshop/generator-assets/commit/1e7c5cba796d1caa0ed80cff367b0037809719d0) from the assets v2 branch. 

Also fixes the name of the assets directory in the adjustment-layer-1 test.

All tests pass on HEAD in the master and iwehrman/v2 branches.