Updated docs

The root is now automatically detected, no need for the RegisterRoot(…

…) api anymore.

if string is null or undefined, return an empty string

new methods for 2FA auth. Split the authentication process into two v…

…erify/login methods. Updated the docs.

- Added support for the special 500 internal error message

- Added support for PHP 7.x

added signature support for email

removed email external template file, added email signatures

version 2.0.0

added documentation for the TinyPHP class itself