Project references provide the wrong name for the implementation dll if the RootNamespace is different from the ProjectName.

We set the Implementation for a WinMD reference to:

```
<Implementation Condition="'$(TargetExt)' == '.dll'">$(WinMDImplementationPath)$(RootNamespace)$(TargetExt)</Implementation>
```

while it should be set to:

```
<Implementation Condition="'$(TargetExt)' == '.dll'">$(WinMDImplementationPath)$(TargetName)$(TargetExt)</Implementation>
```
