Introduced FeedUri class

- Replaced InvalidInterfaceIDException with UriFormatException
- Renamed FeedID properties and arguments to FeedUri
- Renamed InterfaceID properties and arguments to InterfaceUri
Always prepend file:/// when constructing FeedUris to work around a Mono bug

new Uri("/some/path").GetComponents(...) will raise a SystemException on Mono.
new Uri("file:///some/path").GetComponents(...) works.
Installer: Install .NET Framework 4.0 instead of 2.0
Replaced LinqBridge with .NET Framework 3.5
Switched NanoByte.Common to .NET 3.5