Adding page names to all endure pagesets

tools/perf/page_sets/gmail_alt_two_labels.json

 {
   "description": "Chrome Endure test for GMail.",
   "archive_data_file": "../data/gmail_alt_two_labels.json",
   "credentials_path": "../data/credentials.json",
   "user_agent_type": "desktop",
   "pages": [
     {
       "url": "https://mail.google.com/mail/",
+      "name": "gmail_alt_two_labels",
       "why": "Alternate between Inbox and Sent Mail",
       "credentials": "google",
       "navigate_steps" : [
         { "action": "navigate" },
         { "action": "wait", "javascript": "window.gmonkey !== undefined && document.getElementById('gb') !== null" }
       ],
       "endure": [
         {
           "action": "click_element",
           "selector": "a[href=\"https://mail.google.com/mail/u/0/?shva=1#sent\"]"
         },
         { "action": "wait", "condition": "href_change" },
         { "action": "wait", "seconds": 1 },
         {
           "action": "click_element",
           "selector": "a[href=\"https://mail.google.com/mail/u/0/?shva=1#inbox\"]"
         },
         { "action": "wait", "condition": "href_change" },
         { "action": "wait", "seconds": 1 }
       ]
     }
   ]
 }