publish-iis needs to understand portable vs. self contained apps

[moozzyk]

Currently publish-iis always sets processPath attribute to the exe - e.g. (processPath="..\myapp.exe"). If the application is using the shared runtime there will be no .exe and the config file should look differently - processPath="dotnet" arguments="..\myapp.dll"

Note that IIS runs using its own account and dotnet may not be on the path/accessible - we will probably need some guidance about this.
/cc @danroth27

[moozzyk]

Fixed in 1410a5a