JCBC-215: Refactoring viewmode property loading.

This changeset refactors the viewmode property loading by using
the recently added CouchbaseProperties class. This makes it simpler
and more flexible to use. As of now, both "viewmode" and the
preferred "cbclient.viewmode" property names can be used.

Change-Id: Ie845ff0aeb4cbe4d0b0f51e7a21f0ba2367d3011
Reviewed-on: http://review.couchbase.org/24011
Reviewed-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>