Changed util.config_changed to allow identifier (per plugin/task), so several config_changed objects can appear in one uptodate field of a task.
Changed '__' to ':' and prepending 'nikola.' to every new use of utils.config_changed.
Now using correct paths.
Fixed spelling.
Forgot sitemap plugin.
Fixed implementation of TemplateHookRegistry's hash function.
Added information about the change to utils.config_changed (#1526).
Merge pull request #1526 from felixfontein/dependency_refactoring

Refactoring util.config_changed and its usage in core plugins