Blender Git Loki

GP: Add support for Wireframe mode

When enable Wireframe mode in the shading type, all strokes are displayed as simple 1 pixel lines.

The color of the line is equal to the stroke color or the fill color if the fill is enabled and the stroke is disabled or has invisible alpha value.

In wireframe mode, all FX are disabled because sometimes the effects can make the lines invisible.

The modifiers are not disabled.

Still pending to decide if we must add support for Random colors, but not sure if this is useful in 2D.