docs: document SocketFactory(Properties) (#1696)
docs: document SocketFactory(Properties) (#1696)

Document that in addition to the no-args and the deprecated String arg
constructors, a SocketFactory can, like the SSLSocketFactory
constructor, accept a Properties object, as the there otherwise is no
documented, non-deprecated way of customizing the factory.
jorsol/pgjdbc,sehrope/pgjdbc,davecramer/pgjdbc,jorsol/pgjdbc,davecramer/pgjdbc,sehrope/pgjdbc,pgjdbc/pgjdbc,marschall/pgjdbc,sehrope/pgjdbc,davecramer/pgjdbc,jorsol/pgjdbc,davecramer/pgjdbc,AlexElin/pgjdbc,AlexElin/pgjdbc,AlexElin/pgjdbc,marschall/pgjdbc,marschall/pgjdbc,pgjdbc/pgjdbc,pgjdbc/pgjdbc,sehrope/pgjdbc,marschall/pgjdbc,jorsol/pgjdbc,pgjdbc/pgjdbc