model skin object to store and save customisable model elements
give each ship a skin
make the spinners take a skin
make SetLabel modify the ship skin
color->lua conversion method
scenegraph lua setup and model stubs
skin ships in the shipyard
randomise colour on new ships
expose ModelSkin to Lua
get the skin through to the model spinner
implement (most) Lua ModelSkin methods
implement SetColors
choose from available patterns for shipyard ships
show label on shipyard ships
Cargo container model
Merge branch 'model-skin'

Conflicts:
	src/Ship.h
Merge remote-tracking branch 'luomu/cargo-model'