Use "hierarchical" form of RFC 2396 syntax

[ppkarwasz]

The current specification:

• defines the canonical representation of a PURL as pkg:<opaque_part> (using RFC 2396 syntax).
• instructs parsers to ignore all solid / characters between pkg: and the start of a namespace.

For languages like Java that don't have an RFC 3986 implementation this means that it is up to the parser to split <opaque_part> into a path, query and fragment.

Would it be possible to change the spec to use pkg:/<hierarchical_part> as canonical representation? This would simplify the reusage of existing language parsers.

Note: I am aware that PURL is defined in terms of RFC 3986, for which the leading solid / does not have any influence on the syntax, but it has an influence for RFC 2396.