Canonical interwiki prefixes/Proposed extension

It is proposed that a site, e.g. WikiIndex, have an extension that does the following:

• add iw_modified field to interwiki table; this will be the timestamp of when that row was last modified.
• add interwiki_deleted table; this will track interwiki prefixes that have been removed from the interwiki table.
• add interwiki_conflicted table; this will track interwiki prefixes that are inactive because they conflict with a prefix that is currently active in the interwiki table.
• add iwstart parameter to API so that the user can retrieve interwiki modifications starting with a particular timestamp.