Improve label picking (#1179)

* add simple error message helper

* port all label name pickers to use the new LabelInput component

* use pure components where possible

* cleanup

* more cleanup

* lint

* change new label prompt

client/src/components/autosave/filenameDialog.js

@@ -74,7 +74,7 @@ class FilenameDialog extends React.Component {
             color: Colors.ORANGE3
           }}
         >
-          {"Name cannot be blank"}
+          Name cannot be blank
         </span>
       );
     } else if (err === "characters") {
@@ -87,7 +87,7 @@ class FilenameDialog extends React.Component {
             color: Colors.ORANGE3
           }}
         >
-          {"Only alphanumeric and underscore allowed"}
+          Only alphanumeric and underscore allowed
         </span>
       );
     }