The NSIS package includes all the required applications, examples, headers and libraries.
The NSIS build folder is set to `build/winpackage` to avoid littering the main
build directory.
The artifact paths are corrected to avoid the warnings at the end of the
GitLab-Runner build log:
```
WARNING: build/bin/Release/*.dll: no matching files
WARNING: build/bin/Release/*.exe: no matching files
```

Related to #133