Add several doc scripts + doc improvements

- Add Git SHA1 to project semantic versioning in docs
- Add Git SHA1 to file version in docs
- Add scripts to automatically link to OpenCL functions API URL
when an OpenCL function is mentioned in the docs
- Make previous feature optional, because it's slow and may not
work on all platforms
- Set version to 2.0.0-alpha.1 (2.0.0-alpha.1+gitsha1 in docs)