Big update of the OpenChange akonadi resource.

This resource can now download a Contact (essentially an address book entry) from the Exchange server and present it as a KABC::Adressee object. Renders OK in akonadiconsole.

Also add in the start of a decompressor for the compressed RTF that is found in several places in Exchange RPC data.
This is being ported from code that mostly does the same thing, but definitely needs more work before being deployed.