Implement a QML package management mechanism

Almost all popular dynamic languages/frameworks have their own package systems. This can help developers collaborate more easily and avoid duplication works.

A package description file could be a package.json or package.qml, the content can reference the CommonJS package spec(wiki.commonjs.org/wiki/Packages/1.0), at lease the following fields should be included:
1. name
2. version
3. description
4. maintainers/authors/contributors
5. license
6. links(homepage, repo, etc)
7. deps