Add password protection

[jdgregson]

If an attacker suspects that Beamgun is in use, they would be able to disable it with as few as 3 clicks. There should be an option to prevent changes to the following things without a password:

• The "Exit", "Reset", and "Clear alerts", and "Disable for 30m." buttons
• All check boxes
• All settings

Ideally the user should be able to choose which settings to protect.

[jdgregson]

Though this won't protect against an attacker who ends the Beamgun task through Task Manager.