One Watcher to rule them all

__when a folder in /content is added__
- [ ] crawl structure and add new pages

__when a folder in /content is removed__
- [ ] remove the url and all of its children from the map of available urls

__when a template is added__
- [ ] read and register as partial and template

__when a template is changed__
- [ ] the template must be re-read, an re-registered as a template and partial
- [ ] all pages using the template must be re-rendered
- [ ] all pages using a template that uses it as a partial must be re-rendered

__when a template is removed__
- [ ] remove the template from the registry, and partial if possible (maybe replace with an error function?)
- [ ] trigger template change, and let the missing template error come from the page render job

__when a content textfile is changed__
- [ ] trigger crawler to crawl parent page node and queue render

__when a content textfile is removed__
- [ ] trigger crawler to crawl parent page node and queue render

__when a content textfile is added__
- [ ] trigger crawler to crawl parent page node and queue render

__when a stylesheet or any of its imports changes__
- [ ] trigger new app bundle render

__when a app bundle or any of its dependencies changes__
- [ ] trigger new app bundle render

__About always rendering all meta nodes in a folder if one of them changes:__ a coming feature of asimov.js is inheritance of properties between content meta nodes. And when that is implemented, all meta nodes will automatically inherit from the default language meta node.