Previously, there was only one method to get the shadow from a single light in EEVEE in the shader by using the separate RGB node (https://youtu.be/TpWI2rU8iF0?t=871) and it was limited to a maximum of 3 lights while eevee could support up to 128.
This patch adds a new "Light Info" node that is analogous to the old Blender internal's "Light Data" node and its main use is to expose individual shadows and vectors from the lights for use by the artist.
This node should be extremely useful for NPR artists and allow for the creation of shaders and lighting models form scratch that simply weren't possible before such as half Lambert with more than 3 lights and shadows.
Unfortunately I have no idea of how to add the same feature to cycles, so it's a EEVEE only node for now, just like Shader To Closure.
