Make session timeout configurable

[saubyk]

Session timeout is currently a preset value of 60 min duration, which may not meet every user's application need. Instead the timeout can be made a config parameter which should be made available under the Settings menu on the Application tab.

The parameter should have a default value of 60 mins (which preserves the current behavior) with the options of 5 min, 15 min, 30 min, 60 min, 120 min and 'Unlimited' to choose from. If the option Unlimited is chose by the user, the session will not timeout at all.

We should add a warning for the user on the UI, that choosing Unlimited is an unsafe setting and should only be selected if the user is absolutely sure of what they are doing.