Bug 974589 - [contacts] Contacts needs open activity to support text/vca...

...rd because bug 887663 added it to the MimeMapper so email thinks they are downloadable
here the algorithm should be:

```js
var numContacts = 0;
var cursor = reader.getAll();
var firstContact;
cursor.onsuccess = function(event) {
 var contact = event.target.result;
  if (contact) {
    if (numContacts === 0) {
      firstContact = contact; 
    }
   else {
     if(firstContact) {
       renderContact(firstContact);
      firstContact = null;
    }
    renderContact(contact);
 
     numContacts++;
    cursor.continue();
 }
else {
  if(firstContact) {
    renderOneContact(firstContact);
  }
}
```