CCBC-454: Provide clearer API on obtaining host/port information

Rather than the naive lcb_get_host/lcb_get_port() API calls, this patch
introduces a new function called lcb_get_node() which returns a single
node in host:port format. This function accepts options indicating what
type of node to return and under what circumstances should it be
returned.

lcb_get_host() and lcb_get_port() are marked as deprecated now

Change-Id: I031559a5eb6403198d1938660a2477cc1364f237
Reviewed-on: http://review.couchbase.org/38810
Tested-by: Mark Nunberg <mnunberg@haskalah.org>
Reviewed-by: Brett Lawson <brett19@gmail.com>