* Add special field markers to fill a column in SQLStorage with default values
* Add a safeguard to DBCStorage::EraseEntry, Add helper function DBCStorage::InsertEntry to store content
Note: If required similar adjustments to DBCStorage might be reasonable if required
(based on 400's commit 0f37423)
(based on 400's commit 636cfef)
(based on 400's commit 0bbe3a7)
(based on 400's commit ce86b56)
(based on 400's commit b74c6a8)
