Add a new method to create a copy of a graph instance, relying on
chaining serialization and deserialization operations.
Add test suite to validate its behavior, and the underlying serialization processes.
Add a new serializer class to manage partial graph serialization logic,
ensuring to remove link expressions on attributes refering to nodes
that are not in the subset of nodes to serialize.
When creating a compatibility description for an unknown attribute, do not
consider a link expression as the default value for a File attribute.
This is breaking how the link expression solving system works, as it's resetting
the attribute to its default value after applying the link.
If that expression is kept as the default value, it can be re-evaluated several
times incorrectly.
Added a test case that was failing before that change to illustrate the issue.
Extract the logic of importing the content of a graph within a graph instance from
the graph loading logic.
Add `Graph.importGraphContent` and `Graph.importGraphContentFromFile`
methods.
Use the deserialization API to load the content in another temporary graph instance,
to handle the renaming of nodes using the Graph API, rather than manipulating
entries in a raw dictionnary.
