fix invitation and registration to use lowercase

mongoDB.js

@@ -73,7 +73,7 @@ const getDB = new Promise((resolve, reject) => {
         DB.newInvitation = (userid, name, email)=>{
             const invitation = {
                 responsable: new mongo.ObjectID(userid),
-                email,
+                email: email.toLowerCase(),
                 name,
                 ts: new Date()
             }
@@ -88,6 +88,7 @@ const getDB = new Promise((resolve, reject) => {
         };
 
         DB.getInvitation = (email)=>{
+            email = email.toLowerCase();
             return DB.invitationCol.findOne({email}).catch((err)=>{
                 console.log(err);
                 return "System Error";