Allow target instances to be excluded from pattern specifiers

[bocchino]

Currently you can write a pattern specifier that connects to all available targets, like this:

command connections instance cmdDisp

or you can connect to selected targets like this:

command connections instance cmdDisp {
  instance1
  instance2
  instance3
}

It seems useful to connect to all but a few selected targets, like this:

command connections instance cmdDisp exclude {
  instance1
  instance2
  instance3
}

Exclusion actually seems more useful than inclusion here, as we typically want all or all but a few of the available targets to follow the pattern.