WIP: Features for linking artifacts to publications and authors to publications

Fixes

Partially addresses #122 (closed)

Description

Set of features for linking artifacts to publications and authors to publications in a number of ways.

Type of PR

This PR is a feature.

Technicalities

There are 3 ways for linking artifacts to publications:

1. Through the selected publication. (Artifacts can be linked to a particular publication through edit feature of that artifact)
2. Through the selected publication. (Publications can be linked to a particular artifact through edit feature of that publication)
3. Through the view page for all links. (Any publication can be linked to any artifact through the edit feature)

Authors-Publications linking has a similar structure.

Tests

For Artifacts-Publications link, steps for testing each of the above 3 ways:

1. /admin/artifacts-publications/add/1/<publication_id>
2. /admin/artifacts-publications/add/2/<artifact_id>
3. /admin/artifacts_publications

Similarly, for Authors-Publications link:

1. /admin/authors-publications/add/1/<publication_id>
2. /admin/authors-publications/add/2/<author_id>
3. /admin/authors_publications

Note - The features are made based on the modified database structure cdli_db_final_schema. For testing, load the artifacts_publications, editors_publications and authors_publications tables from the new database.

The features are ready for testing.