Implement all Godot Variant types in Go.

[ShadowApex]

Currently we support basic Godot variant type like godot_string, godot_int, etc. We need to finish implementing the other types as their own Go structures that wrap around the underlying variant.

[pastaq]

Working on Vector2/Vector3.

[pastaq]

Vector 2: https://github.com/ShadowApex/godot-go/pull/14

[pastaq]

Vector3: https://github.com/ShadowApex/godot-go/pull/15

[ShadowApex]

@pastaq I noticed some errors after pulling in your code. Here's the problems I see a lot:

func (v *Vector2) Abs() Vector2 {
    var newVec2 Vector2
    newVec2.vector2 = C.godot_vector2_abs(v.vector2)

    return newVec2
}

The C.godot_vector2_abs() function returns a C.godot_vector2 object, not a *C.godot_vector2. It should instead be implemented like this:

func (v *Vector2) Abs() Vector2 {
    var newVec2 C.godot_vector2
    newVec2 = C.godot_vector2_abs(v.vector2)

    return &Vector2{vector: &newVec2}
}

[pastaq]

Fixed https://github.com/ShadowApex/godot-go/pull/16

[pastaq]

Basis: https://github.com/ShadowApex/godot-go/pull/17

[pastaq]

Quat: https://github.com/ShadowApex/godot-go/pull/20

[pastaq]

Rect2, Rect3, RID update: https://github.com/ShadowApex/godot-go/pull/21

[pastaq]

Color: https://github.com/ShadowApex/godot-go/pull/22