adding login form to example

- authentication config supported
- overriding engine.io endpoint supported
- db write access limited to authorized users in example
- authentication implemented in example
- example needs session management to keep track of logged in status
adding level-session dep and moving example related deps to bottom
redirecting to index after login
working db login
login working

- alert on failed login attempt
- login form is disabled after successful login
alerting user of illegal write attempt