Improved exception reporting for dependency resolution failure

- Don't fail attempting to determine task dependencies if prebuilt library file not set or doesn't exist
  - Validate at time that file collection is resolved, not when it is created
- Fail more nicely when project referenced in dependency does not exist
- Resolution exceptions are now @Contextual

Note: Native binary dependency resolution is still just a placeholder for a more complete solution.
Added sample for prebuilt libraries
Use correct syntax for windows DLL export