Use the type of a variable for tab expansion

It would be useful if 
```powershell
[Diagnostics.Process[]] $p = Get-Process
$p | % Prio<tab>
```
would tab complete in the same way as
```powershell
Get-Process | % Prio<tab>
```
Even nicer would be if 
```powershell
$p = Get-Process
$p | % Prio<tab>
```
worked too. (Maybe getting the ArgumentTypeConverterAttribute from the OutputType?)




