Currently, LDAPConnectionOptions stores a vector of strings for the list of hosts where the string is a "host[:port]" combination. 

A new class should be create named LDAPHost. LDAPHost should have a method parse(StringData host, bool isSSL) to parse a host[:port] combination. It should have methods for serializing to HostAndPort and to URI.

LDAPConnectionOptions:parseHostURIs should return a vector of LDAPHost now.