ensure that new users use Gravater in default

lib/models/user.js

@@ -581,6 +581,7 @@ module.exports = function(crowi) {
 
           newUser.email = email;
           newUser.setPassword(password);
+          newUser.isGravaterEnabled = true;   // Gravater enabled in default
           newUser.createdAt = Date.now();
           newUser.status = STATUS_INVITED;
 
@@ -657,6 +658,7 @@ module.exports = function(crowi) {
     newUser.email = email;
     newUser.setPassword(password);
     newUser.lang = lang;
+    newUser.isGravaterEnabled = true;   // Gravater enabled in default
     newUser.createdAt = Date.now();
     newUser.status = decideUserStatusOnRegistration();