====== Array CheckPages ======
Used to check the availability of the various pages before running the task.

May be considered as a property of  the root object, or a property of one of the Item objects
===== Structure =====
<code javascript>
"CheckPages":[
  {
    "Page":"<aPage>",
    "ExpectedIP":"<aExpectedIP>",
    "IncludedText":"<aIncludedText>",
    "UserAgent":"<aUserAgent>"
  },
  {
    "Page":"<aPage>",
    "ExpectedIP":"<aExpectedIP_2>",
    "IncludedText":"<aIncludedText_2>",
    "UserAgent":"<aUserAgent_2>"
  },
  ...
  {
    "Page":"<aPage>",
    "ExpectedIP":"<aExpectedIP_N>",
    "IncludedText":"<aIncludedText_N>",
    "UserAgent":"<aUserAgent_N>"
  }
]
</code>
==== Attributes ====
^ Attribute ^ Use ^ Presence ^
|<aPage>|verifiable page |Required|
|<aExpectedIP>|alleged IP host page|Optional |
|<aIncludedText>|text which contained in the page source code |Optional |
|<aUserAgent>|User-agent, is used to download the source code of the checked page|Optional |
===== Description =====
If non-empty array CheckPages was detected in an external source , then before the task will be executed,  the availability of pages will be checked  in accordance with the elements of the array.

Checking of pages is executing in several stages:
  - If the host where the page located is available.
  - If the host IP coincides with aExpectedIP or aExpectedIP and equal '0.0.0.0'.
  - If AIncludedText  not empty string, the source code of the page is loaded using aUserAgent (redirects are not supported!). If aUserAgent is empty, then used User-agent, installed for your browser. If the source code of the page contains aIncludedText or aIncludedText - empty string.

No more than five first pages will checked.
If the checking at **each** stage is successful, the task continues to execute, otherwise the task is terminated.
===== Examples =====
  - <code javascript>
{
  "Items":[
  ...
  ],
  "CheckPages":[
    {
      "Page":"habrahabr.ru"
    }
  ]
}
</code>
  - <code javascript>
{
  "Items":[
  ...
  ],
  "CheckPages":[
    {
      "Page":"habrahabr.ru",
      "ExpectedIP":"178.248.233.33"
    }
  ]
}
</code>
  - <code javascript>
{
  "Items":[
    {
      ...
      "CheckPages":[
        {
          "Page":"habrahabr.ru",
          "ExpectedIP":"178.248.233.33"
        }
      ]
      ...
    }
  ]
}
</code>