#96 - Build samples
Only build samples if samples dir exists.
Updating config to create release NuGet.config and phantom merge as part of update-release
Get extra build and restore options from environment
- helps w/ #123
- e.g. with the following in makefile.shade, run `build set-quiet default`
```
#set-quiet
  @{
    E("K_build_options"," --quiet");
    E("K_restore_options"," --quiet");
  }
```