New design.

viewport renamed to camera, new drawable canvas/viewport created.
Added ZValue.

Also changed datatype of Pos to FVector from LinearAlgebra.
Added background image property.

Can be used as a map for top down stuff, or wallpaper for sideways
stuff.
Added beginning of the camera class.

Updated description in design also :)
Cleaned up "using" statements.
Viewport based on Panel.

Added layer structure and default constructor.
Updated csproj file.
Merge pull request #15 from martinnj/2D-unstable

2 d unstable