Simple syntax for partial application

Often I want to partially apply a method, which is clumsy in VB because you have to declare all the other parameters and pass them along:
```vb
Function Foo(bar As String, baz As Integer, qux As Boolean, quux As Date)
...
End Function

Dim partiallyAppliedFoo = Function(baz As Integer, qux As Boolean, quux As Date) Foo("predefinedBar", baz, qux, quux)
Dim result = partiallyAppliedFoo(1, True, Now)
```
Can we add a partially-apply operator? Maybe `...`
```vb
Dim partiallyAppliedFoo = Foo("predefinedBar", ...)
Dim result = partiallyAppliedFoo(1, True, Now)
```

Or maybe we should use the Partial keyword to make it clear to new users.
```vb
Dim partiallyAppliedFoo = Partial Foo("predefinedBar", ...)
```
We probably don't even need the ellipsis anymore:
```vb
Dim partiallyAppliedFoo = Partial Foo("predefinedBar")
```
(Since we're in VB, the Partial keyword will also make things more clear for `Sub`s, which don't return a value and so can't be used in an expression, and so `Dim x = FooSub(oneValue, ...)` looks somewhat awkward, since it isn't clear that here the partial application yields a value (delegate), whereas `Dim x = Partial FooSub(oneArg) is much more clear.

(N.B. If you aren't familiar with partial application or why anyone would want to use it, feel free to read up on it; sorry I haven't had the time to explain or motivate over here.)
(N.B.B. The TypeScript team took the approach of strongly-typing JS's existing `arguments` array as a tuple, then using ES6's existing rest operator to pass them along in the right spot, but I'm not sure this is worth doing for VB. This way is much simpler.)