[IndexedDB] Allow renaming/reversioning databases (#53)

(The ability to rename stores/indexes was recently added to the ED)

Use case (c/o the [Lovefield](https://github.com/google/lovefield) team:

* a migration is needed from "old style" storage to "new style" storage. Rather than reversioning, it is easier in some cases to want to atomically rename the database, e.g. "this is now name:Bar at version:2" as part of the upgrade.
* also applies to a "restore" 

Needs design!

* requested as part of the upgrade transaction?
* fail the TX if the database by the new name already exists?






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Reply to this email directly or view it on GitHub:
https://github.com/w3c/IndexedDB/issues/53