Add option to have limited-visibility (stealth) mode

[Adam P]

Users in public environments (internet cafes, etc.) should be able to easily hide the fact that they are using Psiphon (i.e., breaking the law).

In the current floating design, the Bluebar is always visible. In the proposed embedded redesign there are plans for a floating element. These give away to the casual observer than the user is using Psiphon.

There should be an option to hide such permanently-visible elements.