Another round of polishing (#101)

* Implement basic refactorings

* Simplify some match statements

* Rename `ix` to `index`

If we're not going with a single letter name,
then a full word makes more sense.

* Rename `as_hex` to `to_hex`

`as_` implies lossless reinterpretation
while the function does a conversion that loses information

* Replace `for_each` with for loops

for loops are a lot easier to read and maintain.

* factor out x and y coords in Line::render

this is arguably more ergonomic

* Remove redundant `format!(format_args!())`

core/document/src/layers/line.rs

@@ -20,14 +20,9 @@ impl Line {
 
 impl LayerData for Line {
 	fn render(&mut self, svg: &mut String) {
-		let _ = write!(
-			svg,
-			r#"<line x1="{}" y1="{}" x2="{}" y2="{}" {} />"#,
-			self.shape.p0.x,
-			self.shape.p0.y,
-			self.shape.p1.x,
-			self.shape.p1.y,
-			self.style.render(),
-		);
+		let kurbo::Point { x: x1, y: y1 } = self.shape.p0;
+		let kurbo::Point { x: x2, y: y2 } = self.shape.p1;
+
+		let _ = write!(svg, r#"<line x1="{}" y1="{}" x2="{}" y2="{}" {} />"#, x1, y1, x2, y2, self.style.render(),);
 	}
 }