Add support to specify the number of ads a user has blocked in the notification repository

[wspee]

Background

For our upcoming cross promotion campaign we want to be able to show notifications to users that blocked a specific amount of ads.

What to change

Add support to specify the number of ads a user has blocked by adding a minimum and/or maximum number.

Notification repository format:

inactive = no

severity = normal
title.en-US = Test
message.en-US = Test
target = extension=adblockpluschrome blockedTotal>=10 blockedTotal<=100

Resulting notification.json:

{
  "notifications": [
    {
      "targets": [{
        "extension": "adblockpluschrome",
        "blockedTotalMin": 10,
        "blockedTotalMax": 100
      }],
      "id": "1",
      "message": {
        "en-US": "Test"
      },
      "severity": "normal",
      "title": {
        "en-US": "Test"
      }
    }
  ],
  "version": "201707281538"
}

[trev]

I've updated the suggested format as mentioned in #5459 review.

[wspee]

Made notification repository specification also use camel case to be consistent with the rest of the target notation.

[abpbot]

A commit referencing this issue has landed:
​Issue 5457, 5458 - Added support for locales and blocked total to notification parser...

[Ross]

Wrong ticket.