Moved `View` impl methods to trait

Closes https://github.com/PistonDevelopers/graphics/issues/715
Renamed `View` to `RelativeViewTransform`

Closes https://github.com/PistonDevelopers/graphics/issues/717
Added Rectangle
Added RectangleBorder
Added Line
Added RoundBorderLine
Added BevelLine
Added RoundRectangle
Added RoundRectangleBorder
Added BevelRectangle
Added BevelRectangleBorder
Added SquareLine
Added Ellipse
Added EllipseBorder
Added Image
Added color to Image
Added ImageRectangle
Added some modifiers
Merged ellipse
Added some modifiers for Ellipse