Change connect() signature to take a URL.

Since we are connecting to a REST endpoint, I think it is most sane to let the user supply a URL when doing a connection to Couchbase:

couchbase_connect($url); and new Couchbase($url);

An $url would be parsed into

http[s]://[user:pass@]hostname[:port][/bucketname]

i.e. $proto = http / $user = null / $pass = null / $host / $port = 8091 / $bucket = default

The only required part is the hostname

$proto is null | (string) http | (string)https
$user is null | (string) username
$pass is null | (string) password
$host is (string) hostname or IP
$port is null | (int) TCP port
$bucket us null | (string) bucket name

if $proto is != null, append ://
if $user is != null, append : and require pass to be != null, append $pass, append @
if $port is != null, prepend :
if $bucket is != null, prepend /

I hope this covers all cases.