KataBankOCR User Story 1

User Story 1 at http://codingdojo.org/cgi-bin/wiki.pl?KataBankOCR 1. Define a function which retrieves text of a single digit with specified index in text of a number. 2. Make a sequence of texts of each digit of account number. 3. Find indices of text of 0 to 9 digit which satisfies structural equality to them.