When adding a new folder it is created inside the currently active
one. The user is returned to the previously active folder page,
which shows the added folder.
This adds a new route to the add template/folder views. Thankfully,
`url_for` recognizes when `template_folder_id` is `None` and will use
the URL without `/folders/...`, so users without folder permissions
should be unaffected by this change.
The add new templates page now has option to add template folders.
Tweaked wording of other options and h1 to clarify options since it's
not all about templates any more.
Added api client and stuff for it
