Deleted packages shouldn't be searchable or browsable

[dread]

A package in deleted state doesn't show to general users, but admins DO see them. The idea is that they can resurrect them if they want. But now we have the trash can that lists deleted packages. So we don't want admins to see the deleted packages anywhere else.

(But an admin should still be able to READ and EDIT a deleted package, so if he clicks on it in the trash list he can see it to decide whether to resurrect and actually be able to change its state.)

Same in the Web interface and API.

This ticket ties in with #948 highlighting a package being deleted (when viewing or editing) and follows on from the introduction of the trash can #1076.