Update mustache4dart and clean up templates (#1540)

* Import templating cleanups from canonicalization overhaul

* Fix regression in Field appearance on edge cases

* dartfmt

* Add tests

* regenerate test package docs

* Review comment

Author: jcollins-g

lib/src/element_type.dart

@@ -15,7 +15,9 @@ class ElementType {
   final ModelElement element;
   String _linkedName;
 
-  ElementType(this._type, this.element);
+  ElementType(this._type, this.element) {
+    assert(element != null);
+  }
 
   bool get isDynamic => _type.isDynamic;
 
@@ -82,7 +84,9 @@ class ElementType {
       } else {
         typeArguments = type.typeFormals.map((f) => f.type);
       }
-      return typeArguments.map(_getElementTypeFrom).toList();
+      return typeArguments
+          .map(_getElementTypeFrom)
+          .toList();
     } else {
       return (_type as ParameterizedType)
           .typeArguments
@@ -129,6 +133,11 @@ class ElementType {
     // can happen if element is dynamic
     if (f.element.library != null) {
       lib = new ModelElement.from(f.element.library, element.library);
+    } else {
+      // TODO(jcollins-g): Assigning libraries to dynamics doesn't make sense,
+      // really, but is needed for .package.
+      assert(f.element.kind == ElementKind.DYNAMIC);
+      lib = element.library;
     }
     return new ElementType(f, new ModelElement.from(f.element, lib));
   }

lib/src/html/html_generator_instance.dart

@@ -53,6 +53,9 @@ class HtmlGeneratorInstance implements HtmlOptions {
     await _copyResources();
     if (faviconPath != null) {
       var bytes = new File(faviconPath).readAsBytesSync();
+      // Allow overwrite of favicon.
+      String filename = path.join(out.path, 'static-assets', 'favicon.png');
+      writtenFiles.remove(filename);
       _writeFile(path.join(out.path, 'static-assets', 'favicon.png'), bytes);
     }
   }