Allow adding to the default content model instead of replacing it.
Allow dot and slash notation for data endpoints.
Don't complain about missing `pages` or `posts` directories by default.
Add a `BakeScheduler` to handle build dependencies. Add unit-tests.
Ability to output debug logging to `stdout` when running unit-tests.
Merge changes.
Remove unneeded trace.
Fixes to the `cache` Jinja tag.

* Thread safety, since it stores common data potentially coming from pages
  baked at the same time.
* Correctly capture and restore modifications made to the execution context
  (e.g. sources used in the captured section).
PyYAML supports sexagesimal notation, so handle that for page times.
Improvements to incremental baking and cache invalidating.
More options for the `showrecord` command.
Use the `OrderedDict` correctly when fresh-loading the app config.
Unused import.
Fixed a bug with the `shallow` source. Add unit tests.
Improvements and fixes to incremental baking.

* Better handling of the render pass during page rendering.
* Used sources are paired with the pass they were used in.
* Proper use and invalidation of the rendered segments cache based on render
  passes.
* The `Assetor` is also better tracking what was used in a page.
* Add flags on a page to get better caching information for the debug window.
* Property invalidation of the previous bake record when needed.
* Better information about why pages are delayed.
Add `--log-debug` option.