don't let people delete the delete type

[Aaron Swartz]

Right now it's pretty easy to delete types like http://demo.openlibrary.org/type/delete since the page doesn't say anything and delete seems to work.

[Aaron Swartz (aaronsw)]

All the special types should have notes on their type pages explaining what they're for.

[Anand Chitipothu (anandology)]

I don't think, we can specify permission to not delete a page.
All we can do it let people not have permission to edit some
important types.

> All the special types should have notes on their type pages explaining
> what they're for.

Problem is that we consider all fields in type as schema.
If we define schema as a list of properties and each property is a
thing(name=field_name, value=type, allow_multiple=true/false), then
we can add additional fields in the type like description etc.
This will also solve the ordering problem in schema.
Property here will be something like compound value type seen in
freebase.
Form inputs for properties can be named as property#n.* and edit.POST
can take special care for handling it. All properties can be children
of the type they belong to.