Hide configuration information

[flowchartsman]

allow the user to specify that the config file be securely deleted or the environment variables be cleared when the USB event (or failed password) fires. This will prevent any information being gained from inspecting them.

[flowchartsman]

depends on #9

[flowchartsman]

It should probably be noted that "secure delete" is kind of a misnomer these days. A better option would be to encrypt the config file.