Allow user to lock app with pin or password

[bkerensa]

In celebration of #PasswordDay I am creating this issue and as we think about tour and splash screen UI we should create a lock screen for the app and add functionality to allow user to set a pin or password to add an extra layer of security over their app install so if their device is stolen or used by someone Glucosio can be locked independently of the OS.

[satya164]

Why not just use third-party apps to lock Glucosio?

[bkerensa]

@satya164 because thats a third party app they would need to install and its becoming more common for health apps or finance apps to have their own locking feature.

[DravitLochan]

you need splash screen too?

[danielgomezrico]

Will be cool to support fingerprint too

[vineyugave]

PR created : https://github.com/Glucosio/glucosio-android/pull/319