Migrate series relations to universes

[The4thLaw]

Summary
Rather than series relations, we should have universes connecting the series and albums.

Dependencies
This feature depends on #113 since the format will change quite a lot and the user needs to be warned of potential data loss.

Describe the feature you'd like
Universes would have:

• A title
• A description
• A logo that can be filled with drag-and-drop
• A URL

Series and albums could have one universe. If not specified, albums inherit the universe from the series.

Relations could be migrated automatically:

• Browse all series one by one
  • If the series has relations
    • Check if one of the related series is already in a universe (Set). If so, add the current series to that universe. If not, create a new one.
• For each universe (set)
  • Find the largest series (most albums)
  • Create a universe in the database with the name of the largest series and add all links

Checklist

• Flyway migration in Java to properly handle the relations
• Universe - edit
• Universe - view
• Series - edit
• Series - view
• Album - edit
• Album - view
• Export
• Import