Unique php file entry point

Updates to have a unique php file entry point.
index.php is used and can be renamed to what you want ;)

url will look like: 
- index.php?regiter
- index.php?edit
- index.php?password_reset


function  passwordResetLinkIsValid() is renamed as `isPasswordResetLinkValid()`

function passwordResetWasSuccessful() is renamed as `isPasswordResetSuccessful()`

Creation of functions : 
-`isRegistrationSuccessful()`
-`getPHPMailerObject()`