Refactoring of release_info's updatexml engine.
Reimplements version parsing. Adds extensive tests. Removes pm_parse_project_version() and introduces pm_parse_request() and pm_parse_version().
Move bootstrap-based logic out of release_info engine. Now the (parsed) info from the update service could be cached in drush.
Adds the creation time of the extension's .info file to projects. Similar to what update.module does.
Add an outline of a new 'drush' engine for update_info. Just manages caches for now.