Added Flask login package and a secret key

A secret key was required for the application which has been added in a
new file called 'secrets.py', which has been .gitignored.

Changed the requirements list to the order in which it is generated by
pip freeze.
Added User login support

Only the frontend based login has been tested and it works!
The code needs to use raw queries, though.

The flash messages are currently displayed in a very crude form, and
need to be styled.

The frontend directory structure has been changed too to increase
brevity.
Say what!