Included features:
* Creating double list
* Adding at the beginning, the end and specific position of the list
* Removing from the beggining, the end and specific position of the list
* Returning pointer to the first and the last element of the list
* Calculating size of the list
* Checking if the list is empty
* Checking value of the element at the specific index of the list
* Emptying the list
* Displaying from the beginning and from the end
Commands:
0 - Exit the program.
1 - Add element at the end.
2 - Remove the last element.
3 - Add element at the beginning
4 - Remove the first element.
5 - Add element at specific position.
6 - Remove element from specific position.
7 - Display value of the last element.
8 - Display value of the first element.
9 - Check if the list is empty
10 - Check the size of the list.
11 - Remove all of the elements.
12 - Display value of the element at specific position.
13 - Display value of all of the elements.
14 - Display value of all of the elements from the end.