update ActorSheet to ActorSheetV2 and do a general cleanup pass

move editable-input partial into its own file so it doesn't have to be copy-pasted everywhere
change css to use nesting

src/EditableInput.hbs

@@ -0,0 +1,11 @@
+<div class="editable-input editable-{{type}}">
+    {{#if (eq type "checkbox")}}
+        <input type="checkbox" name="{{name}}" {{checked value}}>
+    {{else}}
+        <input type="{{type}}" name="{{name}}" value="{{value}}" placeholder="{{placeholder}}">
+    {{/if}}
+
+    {{#if placeholder}}
+        <div class="placeholder">{{placeholder}}</div>
+    {{/if}}
+</div>