Basic design

[bvssvni]

See https://github.com/PistonDevelopers/piston/issues/587

Using hierarchical contiguous arrays: https://github.com/PistonDevelopers/range/issues/11

Prototype: https://github.com/bvssvni/ld30/

• This library should only deal with geometry, not materials, and be back-end agnostic
• It should not depend on vertex format, but stop at indices level
• Index buffer can be u32 independent of vertex format, converted if necessary to GPU buffer format
• Decoupled structure, using Range<AddTo<T>> or similar for other actions, works as message passing