Add an updateObject operation

Currently it's not possible to update the properties, the content, the ACLs, and the polices with one call. There is just one exception: the checkIn operation takes all of these.
It would nice to have an updateObject operation that could also do that for non-versioned documents and maybe also non-document objects.
There are several use-case where the content and the properties have to be changed at the time. If one operation fails, it's the responsibility of the client to clean up. Many repositories can do that better than the client and may even can use a transaction under the hood.