Added test for behavior of operations on an unconnected SMTP object,

and tests for NOOP, RSET, and VRFY. Corrected typo in a comment for
testNonnumericPort. Added a check for constructing SMTP objects when
non-numeric ports are included in the host name. Derived a server from
SMTPServer to test various ESMTP/SMTP capabilities. Check that a
second HELO to DebuggingServer returns an error. [GSoC - Alan McIntyre]