Fixed bugs with phone number conversion
[note] User must enter only the local part of the phone number when registering, while international dial code is provided automatically by whmcs for selected country.
Major code refactoring

New features:
* Domain registration period support (up to 5 years)

Changes:
* RN number is tied to WHMCS user
* Domain's RN number is independent of user's RN
Fixed bugs in Domreg::requireRegistrant and hooks.php

* New registrants were created in Domreg, but not saved in database
* In hooks.php, if exception bubbles up, everything is skipped, even if there had to be some data.
* Added better logging @ Domreg::requireRegistrant
Changed README