Fixed devices not showing up on subscription page

[Ziver]

The device column in the subscription page only showed ?? as there where no device data stored in the DB, this is fixed in this commit.

Also added an additional column in the subscription page that shows some more info about the registered action, currently only the play position is displayed but it could be extended in the future.

[bohwaz]

Fetching the device ID for each episode action would be too slow, as we can add thousands of actions at the same time…

[Ziver]

Storing the device ID string would be a alternative but it would take more storage in the DB.