fixed #706 : handling fresh/new user scenario, creates Notebook 1 by default

Assigning the new notebook number based on availability and create 'Notebook 1' in case of new/fresh user login.
when I have Notebooks with suffix [1,4,5,6,10] where Notebook 5 is selected and If I try to create a new Notebook then it creates Notebook 7 (Ideally it should create Notebook 2) so to avoid this I am assigning 1 to the counter(n). Please let me know if it affects something else.