Slight docstring changes.
Starting to add specific test pages for specific page types and annotations.
More generally ignore directories called, _build to also include the builds in the test directory.
Removing DefaultPage since it's no longer needed. Instead we add BasicPage
to the default bundle which matches every page and will be therefore applied
to every page. Other pages won't inherit anymore from BasicPage since they
can now take care of their very specific logic.

Also moving the default_bundle definition to the bundles package and make it
configurable in the conf.py for the documentation.
Using custom bundle for sampledocs in tests.
LongSection annotation.