Add classification to internal data model

[PhilippMa]

Summary of changes

Added classification to internal data model:

• Add field for classification config in resource state
• Add classification field on attributions

Context and reason for change

Upcoming tickets will need access to classification data included in .opossum files.

How can the changes be tested

• Check that files can be parsed and opened without error
• (Optional) log parts of internal state to console after load has finished, check that classification data in internal state is correct

[abraemer]

LGTM