Make `Point` a new type rather than an alias?

[mitchmindtree]

This would be heavily breaking, and may not be worth it, however I think there's a chance it could offer a lot of benefits, especially now that the conversion traits exist (they never used to when conrod first existed).

pub struct Point {
    pub xy: [Scalar; 2],
}

Pros

• It could easily convert between [Scalar; 2] and (Scalar, Scalar) by impling From<[Scalar; 2]>, From<(Scalar, Scalar)>, Into<[Scalar; 2]>, Into<(Scalar, Scalar)>
• We could implement the ops traits for it (we currently have to use vec2_add(a, b) which is ok though a little unwieldy at times as it requires an import and the vecmath crate.
• Stronger type safety. If we were to do the same for Dimensions, it would be much harder to accidentally pass arguments the wrong way around (which I have done a couple times heh).
• We can add any convenience methods as we think of them.

Cons

• It would be a heavily breaking change.
• Would require quite a bit of work, though it would generally be very easy work.

[bvssvni]

Maybe use the shapes library?