[BUG] v-table chokes search middleware with multiple sort parameters

[mryellow]

When not given a $props.sort the created life-cycle hook will default $props.sort to $props.rowKey which is itself defaulted to _id.

When given a url containing a sort query-string this will then result in 2 sort params being sent to the server.

sort=from-url&sort=_id

Which the search middleware will see as sort === ['from-url', '_id'] and will choke trying to replace - strings.