Video: Add utility to work with cookies.

Adds utility that provides convenient way to work with cookies.

API:
  - clear - empties the storage.
  - getItem - returns the current value associated with the given name.
  - key(`n`) - returns the name of the `n`th key in the list.
  - removeItem - removes the current value associated with the given name.
  - setItem - adds new value to the storage or rewrites existent.

@auraz,  @valera-rozuvan please review.