Minor Bugs and Admin Toggle Feature

[harshit-soora]

These are the functions that I have added:

1. A admin toggle on register page for admin , (alternative - this feature could be in-build inside the code with some super user too whose credential are already stored when the system runs.)
2. Students list feature in admin which allow the admin to get details of students who have registered

These are the issues that I have resolve:

1. Admin login doesn't redirect to admin dashboard instead it redirect to normal dashboard
2. Add Book and Remove book have some query error in it which have been resolved.
3. After issue book the list show author and book name as empty (added a join query to resolve that)
4. Remove book have similar error where the drop down list doesn't have Book and Author name

There were some minor errors/bug in between, I will be adding my work under this issue. You can review and merge it.

One more courtesy, I will be adding the newer version at my Github repo for sure I will promote your work :)

Your coding style was very nice :D