The Forest: 1st pass autofixing surface shaders

Looks like this game is not using the default Unity lighting shaders.
Seems like unitysunshine again, but the CRCs don't all match up with
Dreamfall.
The Forest: Add Shader Headers
The Forest: Symlink standard Unity lighting shaders

Some of these are used by the game - at least the vertex shaders are.
The Forest: Add additional lighting shaders
The Forest: Prepare ini to copy matrices for lighting fix
The Forest: Fix SHADOWS_SCREEN variants
The Forest: Unverified light fix
The Forest: Get MVP + MV matrices from other shaders
The Forest: Add missing declarations

Oops.
The Forest: Fix lighter in cave, and SUBTRACT adjustment in pixel shader

The macro I used to insert these fixes isn't smart enough to find the
start of the matrix multiply, and I missed this one by eye.

Pixel shader adjustment is supposed to be a subtraction - I must have
copied the vertex shader adjustment by mistake.
The Forest: Change rest of pixel shader light fixes to SUBTRACT as well