Consolidation of the GNPy module

Consolidation of the GNPy module

- add GnpyException to manage unexpected events
- expand the 32-bit identification field of fibers to range
from 243.0.0.1 to 243.255.255.255
- expand the 32-bit identification field of EDFAs to range
from 244.0.0.1 to 244.255.255.255
(the 32-bit identifiers are not ipv4 addresses but use the same
dotted-decimal notation. This format is imposed by GNPy yang model to
comply with the IETF recommendations and to be compliant with planning
tools coming from the IP world.)

- code refactoring

Signed-off-by: atriki <ahmed.triki.tn@gmail.com>
Change-Id: Ifa41c68874b8d87abe746cd6c1b87ee950131a32