render: add emission support to non-gbuffer renderers

[kikonen]

Problem: with current logic, gbuffer based light source will burn its' representation mesh due to being too close to light.

And since only g_light can now render miession, it's not possible to render it sensible for lights.

Either,
a) need to figure out how to avoid g_light shader for not causing over burn on,
b) add support for emission render in forward render logic