Document that TimeoutException are wrapped

Every operation documented as throwing a TimeoutException in fact throws
a RuntimeException wrapping a TimeoutException.
Updated javadoc to reflect that.

Change-Id: Iabacb330724cc4dd0f7f393d8eca42965aef38b3
Reviewed-on: http://review.couchbase.org/44525
Tested-by: Simon Baslé <simon@couchbase.com>
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-on: http://review.couchbase.org/44704
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Simon Baslé <simon@couchbase.com>