Inconsistent Fleet Assignment Handling

[larsll]

The assignment of Cars to Fleets is taking place three places:

• Fleets DDB Table; contains an array of cars per Fleet, SSM instance ID stored only.
• Cars DDB Table; contains the ID and Name of the assigned Fleet.
• SSM Tag; contains the ID and the Name of the assigned Fleet.

Even if data is updated into both Cars DDB and SSM at the same time the data in SSM will overwrite the DDB value during status update.

Issue nr. 1:

• When you register a new Car into a Fleet it is not stored in Fleets DDB
• When you use the Edit Device feature to update a Fleet assignment it is not stored in Fleets DDB

Issue nr. 2:

• On the Fleets page, if you assign a Car to a Fleet it is not removed from the old Fleet in Fleets DDB.
• Device DDB/Tags is updated correctly.

The cars array in the Fleets DDB seems to only be used for marking the checkbox next to the car on the Edit Fleets page, so maybe it can simply be removed, and the checkboxes are populated by filtering the list of cars...

If #112 is merged then another issue is also present:

• Deleted cars will still be in the Fleets DDB cars array.