Remove code used by bagit-support

[mikejritter]

Resolves: https://jira.lyrasis.org/browse/FCREPO-3233

• Extracted BagIt classes to a new bagit-support library
• Replaced BagIt classes with the bagit-support equivalents
• Update some of the initialization for BagItDigests to conform to bag profiles correctly when exporting

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Notes

The way the BagItDigest init was updated in the Exporter is to query first for the Manifests-Required, then Manifests-Allowed, then fallback to sha1. For Manifests-Required it makes sense to use each digest algorithm. I opted to do the same for Manifests-Allowed though I'm not 100% about that choice. We could try to alter this by picking a single algorithm to use, or maybe creating an issue to allow the user to specify what algorithm(s) to use (which would require additional validation against the profile, which shouldn't be a big deal).

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Testing

1. Start a fresh fedora repository, e.g. with fcrepo4-docker FEDORA_TAG=5.1.0 docker-compose up -d
2. Create a binary
3. Create a bag-config.yml for export

   bag-info.txt:
   Source-Organization: fcrepo-import-export
   Organization-Address: localhost
   External-Description: Sample bag export for fcrepo-3233

4. Run the exporter

   java -jar target/fcrepo-import-export-0.4.0-SNAPSHOT.jar --mode export --resource http://localhost:8080/fcrepo/rest --dir fcrepo-3233 --binaries --bag-profile beyondtherepository --bag-config bag-config.yml --user fedoraAdmin:secret3

5. Restart the fedora repository, e.g. with fcrepo4-docker docker-compose down; FEDORA_TAG=5.1.0 docker-compose up -d
6. Run the importer

   java -jar target/fcrepo-import-export-0.4.0-SNAPSHOT.jar --mode export --resource http://localhost:8080/fcrepo/rest --dir fcrepo-3233 --binaries --bag-profile beyondtherepository --bag-config bag-config.yml --user fedoraAdmin:secret3

7. Check that all binaries have been reimported