Tighter definition for links, document references & some other things

[hoijui]

Some sample questions - do not try to answer them exactly, I just put them down to outline the field to be further defined here.

• some properties need a URL

• some properties can be a URL or a path (relative to the repo root directory)

• some properties can be a URL or a path (relative to a URL ... the documentation URL, repo root, manifest URL?)

• some properties can be only a path, relative to the repo root (or manifest location?)

• Do we allow ./rel/path/ and rel/path/, or only the later?

• do we allow unicode characters or only ASCII in paths?

• do we allow spaces in paths?

• do we require paths to be URL encoded? ("Hello You" -> "Hello%20You")

• do we want restrictions on allowed characters for names and titles?

• do we want to limit max length of certain strings (like project titles)?

[hoijui]

This is now basically solved, as stated in: https://github.com/OPEN-NEXT/OKH-LOSH_copy/issues/31

All such properties now allow either a web URL (protocol: HTTP(S)) or a repo-/project-relative path, not starting with /, nor containing ./ nor ../

Other then that, we require only Unicode for the relative paths and / as pat-part separator, and URLs need to conform to the official URL specification.