Allow placing printouts in lecterns

- Add a new custom lectern block, that is used to hold the printed
   pages. We have to roll quite a lot of custom logic, so this is much
   cleaner than trying to mixin to the existing lectern code.

 - Add a new (entity) model for printed pages and books placed on a
   lectern. I did originally think about just rendering the item (or the
   in-hand/map version), but I think this is a bit more consistent with
   vanilla.

   However, we do still need to sync the item to the client (mostly to
   get the current page count!). There is a risk of chunkbanning here,
   but I think it's much harder than vanilla, due to the significantly
   reduced page limit.

projects/forge/src/generated/resources/data/minecraft/tags/items/lectern_books.json

@@ -0,0 +1 @@
+{"values": ["computercraft:printed_page", "computercraft:printed_pages", "computercraft:printed_book"]}