common fill: add fill-rule interface.

common fill: add fill-rule interface.

Fill rule is used to select how paths are filled.

For both fill rules, wheter or not a point is included in the fill is determined by taking a ray
from that point to infinity and looking at intersections with the path. The ray can be in any
direction, as long as it doens't pass through the end point of a segment or have a tricky
intersection such as intersecting tangent to the path.

@API Addtions:

enum class TVG_EXPORT FillRule { Winding = 0, EvenOdd };
Result Fill::rule(FillRule r) noexcept;
FillRule Fill::rule() const noexcept;

@Examples:

shape->rule(FillRule::EvenOdd);

@issue: 97

Change-Id: Ia282acd5f9d6154216683c1a65369a9a48220544