Attempt to sanitize the JS code + fix few bugs

Attempt to sanitize the JS code + fix few bugs

The problems solved by this commit:

- When another user logs in during logout timeout, he was logged out
  automatically, even before choosing a coffee.

- Logout timer was not shown always when it should. After choosing a
  coffee, the timer was shown for a while. Then, after the user page
  was reloaded from the server, the timer disappeared and after an
  elapsed second, the timer was shown again.

- Local debug area was not shown and hidden consistently.

The first problem was resolved by canceling the logout timer after
login. The last two problems were fixed by centralizing of the UI
updates to a single function, which does the update based on the value
of state variables.