migration of outdated scene databases

[johntruckenbrodt]

#256 introduced breaking changes to the Archive database structure. With this, the content of outdated databases can now be imported into a newly created database:

from pyroSAR import Archive
db_new = 'scenes.db'
db_old = 'scenes_old.db'
with Archive(db_new) as db:
    with Archive(db_old, legacy=True) as db_old:
        db.import_outdated(db_old)