refactor: Dart analyze and dartdoc fixes

Author: mongoose13

lib/src/area.dart

@@ -146,7 +146,7 @@ class Area extends Measurement<Area> {
   double get asSquareInches => _precise(Area.squareInches._of(si));
 
   @override
-  String toString() => '${asSquareMeters} m²';
+  String toString() => '$asSquareMeters m²';
 
   @override
   Area _construct(final double squareMeters, final Precision precision) =>

lib/src/distance.dart

@@ -184,7 +184,7 @@ class Distance extends Measurement<Distance> {
   double get asNauticalMiles => _preciseOf(Distance.nauticalMiles);
 
   @override
-  String toString() => '${asMeters} m';
+  String toString() => '$asMeters m';
 
   @override
   Distance _construct(final double si, final Precision precision) =>

lib/src/interpreter.dart

@@ -7,10 +7,10 @@ part of fling_units;
 /// will generally only require the built-in converters for the [Measurement]
 /// types being used (e.g. [Distance.miles]), but if needed, some
 /// [MeasurementInterpreter] subtypes can be configured further (e.g.
-/// [AreaConverter]).
+/// [AreaInterpreter]).
 ///
 /// Users should not need to access the internal workings of
-/// [MeasurementConverters], but instead pass them to the appropriate
+/// [MeasurementInterpreter]s, but instead pass them to the appropriate
 /// [Measurement] instances for interpretation (typically via an `as()` method,
 /// such as [Area.as]).
 abstract class MeasurementInterpreter<T> {