It's unclear that primitive type "uri" enclose URNs (not only URLs)

[Kroisse]

Currently, Nirum specification doesn't clarify their implementors to treat "uri" be a union of Uniform Resource Locator and Uniform Resource Name, or accept URL only and reject URN. Because URN is used rarely in practice, most of Nirum users might want to exclude URN during serialization and deserialization. Furthermore, most of programming languages don't have URN datatype in their standard library. It makes hard to implement the runtime for them.

[dahlia]

I suggest to rename uri to url.

[dahlia]

The compiler 0.4 will be released with a new type name url and deprecated uri (which is aliased to url).

In the next minor release we need to obsolete uri.

[dahlia]

PR #281 implemented it.