Store element status in model

Currently the status of an element (Repository, Branch, Revision) is only stored in OIS. It should be available in the model of the element as well.

$repository->getModel()->isDeleted(): bool returns if the repository is deleted
$banch->getModel()->isDeleted(): bool returns if the banch is deleted
$revision->getModel()->isDeleted(): bool returns if the revision is deleted
$repository->getModel()->setDeleted(bool $deleted) sets if the repository is deleted
$banch->getModel()->setDeleted(bool $deleted) sets if the banch is deleted
$revision->getModel()->setDeleted(bool $deleted) sets if the revision is deleted
OIS is not updated automatically if setDeleted is called
The $object->delete() methods set the deleted status correct
An upgrade for existing objects is provided
The repair jobs restores information from the OIS