Fix up the SOVERSION and VERSION in cmake

The SONAME should contain the ABI version, while the VERSION should
contain the specific version, rather than the other way around.

Change-Id: I14116a41f0405c84be444571a24a36f1cc3c506a
Reviewed-on: http://review.couchbase.org/42147
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Mark Nunberg <mnunberg@haskalah.org>