add the MutualBlock flag

[dimaspirit]

Made/Proposed changes:
(Don’t use general words, describe changes in details)

• You can choose a type of blocked logic (Privacy List).
  There is 2 type:
• Block in one way. When you blocked, but you can write to blocked user.
• Block in 2 way. When you blocked and anyone can write to another user.

Does the documentation need an update?

1. https://quickblox.com/developers/Web_XMPP_Chat_Sample#Create_a_privacy_list_or_edit_existing_list
   Add the flag.

// In all cases, blocked user can't write to you.
var users = [
  {user_id: 34, action: "deny", mutualBlock: true}, // it's means you can't write to user (34)
  {user_id: 18, action: "allow"} // it's means you can write to user (18)
];

[soulfly]

I propose to optimise this code, remove duplicates.
We can use nested functions for this.

for example:

function createPrivacyItem(order){
    iq.c('item', {
      type: 'jid',
      value: userJid,
      action: userAction,
      order: order
    }).c('message', {
    }).up().c('presence-in', {
    }).up().c('presence-out', {
    }).up().c('iq', {
    }).up().up();
}

createPrivacyItem(i+1);
createPrivacyItem(i+2);

and also

function createPrivacyItemMutual(order){
  iq.c('item', {
      type: 'jid',
      value: userJid,
      action: userAction,
      order: order
    }).up();
}

createPrivacyItemMutual(i+1);
createPrivacyItemMutual(i+2);

[dimaspirit]

To carry out the function declaration of the loop.
It looks weird