1. Reorganizes libraries
2. Adds new method ArtesiaIngest#apply_teams_asset_file to encapsulate adding xml to ArtesiaIngest#teams_asset_file, generate OpenvaultAsset models for ArtesiaIngest#openvault_assets, and establish relationships between OpenvaultAsset models.
3. Updates teams_asset_file.zoom_sample.xml fixture for more determinate way to identify relationships between <UOIS> nodes (which become OpenvaultAsset models).
4. Adds tests

Closes #75
Closes #76
Overrides ArtesiaIngest#depositor= to apply depositor to all OpenvaultAssets returned by ArtesiaIngest#openvault_assets. Closes #78.