Add a first implementation to build a dictionary of objects from the
network specification.
Improve SpecificationLoader objects in order to load a specification
from a graph and instantiate all the objects according to their type
specification.
Refactored the test to instantiate two more objects in addition to the
previous one.
Write a new test to check the setting of literal properties, up to now
we can handle only property of type double.
Refined the test about literal properties in order to check Identifier
and Comment properties for GasNode.
Add a test for parsing edges and check connections.
Delete a temp file.