Add raw file links to single file headers (#23)

[bryfry]

• Add Raw, Copy Raw, and Download Raw buttons to the file view header bar
• Generate raw files for all blobs (previously only images got raw files), written to raw/{ref}/{path}

[u35253]

Does this work? Improved binary file support would be awesome. Eg, if a PDF is included in a repo, to have that listed and downloadable. Is that what this does?

[antonmedv]

I will need to download it to test it locally first.