Migrate pages into DB

[vphantom]

Right now, it's difficult to upgrade PyriteView itself from repo because even for "stock" installations, some templates are expected to be edited, mainly in the pages/ subdirectory. Those should be editable online instead. This will also add the benefit of them not being in Twig anymore, just regular HTML (Summernote).

The editor will thus have to offer to create versions for each of global.languages, for each page.

The welcome page should become editable in this fashion, not just the 3 thrown in pages/.