defines a new RenderInstType RIT_DecalRoad;

engine:
renderPassManager.h - definition
renderPassManager.cpp - reference string

script (to be included in a secondary PR): \game\core\scripts\client\renderManager.cs will add scripted timing and an additional functionality entry.

immediate purpose: provides a render sorting mechanism specific to decal roads.

long term impact: will also include a basiconly flag used by deferred shading to denote that this will only be rendered using the basic lighting functionality, as opposed to the higher-order advanced lighting mechanisms.