Password prompt choices (#79)

* Implement disco mode

* Add option to hide the password completely

* Update README.md

* Update README with new version of env variables (not yet implemented)

* Fix const-correctness

* Add XSECURELOCK_PASSWORD_PROMPT flag + 3 bonus prompts

* Remove XSECURELOCK_PASSWORD_PROMPT from readme

* Add "REMOVE IN v2" inside XSECURELOCK_PARANOID_PASSWORD setting name

* Revert accidental PARANOID_PASSWORD_MIN_CHANGE change

* Wrap _Static_assert in a macro

* Replace emoji escape codes with actual values

* Rename ShowFromArray function

* Use ++ as prefix operator

* Remove useless parentesis

* Move flag variables inside main

* Update README with samples for the different XSECURELOCK_PASSWORD_PROMPT values