Migration for nested blocks from nocms-pages gem
Adding the regular staff for a new block
We add the setting for allowing nested blocks
Adding a partial for the nested blocks list

It's quite nasty to duplicate the template, but right now I have more serious issues with making the JS work, so first let's make it work annd then we'll make it pretty
Small changes in blocks index for the new JS

Now we need to work with classes, not ids
Template for container with nested blocks
We start editing only root blocks. Other ones should be editable through the blocks tree
Now, we need to sort the blocks both in the admin page and in the front partials

Since we now sort the blocks and have dafault values for positions, we fon't need to force the position, which lead to strange behaviours when sorting blocks
Merge branch 'features/nested-blocks'
nocms-pages and nocms-admin versions