bake: Fix bugs introduced by bake optimizations, of course. - Make the execution stats JSON-serializable. - Re-add ability to differentiate between sources used during segment rendering and during layout rendering. Fixes problems with cache invalidation of pages that use other sources. - Make taxonomy-related stuff JSON-serializable.

[pytest]
norecursedirs = .* _darcs CVS .svn .git .hg *.egg-info dist build bower_components node_modules venv tmp* _cache {args}