WIP - Hull heating shader effect

# Description:
Apply a simple heating shader effect based on the hull temperature and direction of travel.

It adds one texture which controls the heat gradient coloring. If you want to make it fade in later than squash the gradient further up and extand the black section towards the middle. Vice versa with the white end if you want it to ramp up earlier.

# Concerns:
I'm basically spamming the materials applied to *ANY* model since I don't know how to distinguish whether something is a ship or not. This means that buildings, missiles... basically everything gets a heat gradient texture associated with it :( This is a major sucky thing.
There's also the question of ownership of materials and textures, if they're shared then I might have screwed up the fact that each ship has it's own blob of shader data and but sets it to be the specialParamter0 assigned to a single shared material. 

@shadmar you're a shader Ninja :) any advice on the shader itself?

# Testing:
The best way to test is to launch with a powerful ship like the PumpkinSeed and make sure it hasn't got any atmospheric shielding. It's pretty clear when it's getting toasty!

Andy