fixes #2827
cleanup
fix tests
Merge pull request #2835 from digi604/fix-2827

fixes #2827 (moving public pages to unpublished parents)
Add JSON MIME types to HttpResponse in resolve() per digi604's direction

This fixes an issue where the side frame causes redirects to non-sensical URLs of the type: `http://127.0.0.1/en/<html><body>en</body></html>` or similar.
fixes correct descendants language
More updates
fixes #2834
fixes #2833
Merge pull request #2837 from mkoistinen/json_mime_type_for_2788

Add JSON MIME types to HttpResponse in resolve() per digi604's direction
Now using dashed outline 'ghosts' for non-existent titles, nice!
Merge pull request #2838 from digi604/fix-2834

Fix 2834 (page tree expansion preview link)
Merge pull request #2839 from digi604/fix-2833

fixes #2833
Make unpublished parent gray too
Prevents console errors when that.showError doesn't exist.
Merge pull request #2832 from mkoistinen/gray_unpublished_indicators

Instead of a bright red for unpublished, use a light gray
bumps version to 3.0b4.dev12
adds commit hash for 3.0b4.dev12
fixes issue #2815
fixes #2844