Adding capability to delete resources via label selector

@smarterclayton, @bgrant0607  @derekwaynecarr Thanks to have a look when you have time
Suggest combining all of these if statements into a switch/case statement.

```
switch {
case len(filename) > 0 && len(args) == 0:
case len(filename) > 0: // listing all conditions like this makes it clear that as written, the code doesn't do anything for this case!
case len(selector) == 0 && len(extractedArgs) == 2:
case len(selector) > 0:
}
```