Add two new commands, "open" and "close", to open and close ongoing

Add two new commands, "open" and "close", to open and close ongoing
connections to specified services.  (Otherwise a connection is created
and destroyed for every request.)

Main purpose: to be able to use srfsh for database operations that require
transactions.

Warning: typically the <keepalive> value will need to be increased for
the service in question in opensrf.xml, or else the server will close
the connection before you can type your request.

git-svn-id: svn://svn.open-ils.org/OpenSRF/trunk@1725 9efc2488-bf62-4759-914b-345cdb29e865