Give admins the ability to destroy all problems associated with an app

Due to some recent changes in errbit fingerprinting, my apps are littered with Problems that represent the same underlying error, but are not successfully clustered into different Errs of the same Problem by errbit.

I'd like to make fingerprinting more configurable (more to come later), but in the meantime I need to clean up my errbit apps, now that I have worked around the fingerprinting problem temporarily.

This feature is my attempt to enable admins to cleanup an app. It adds a "delete all errs" button to an app's edit screen that performs a one-shot destroy of all Problems. (The alternative is to page through hundreds or thousands of problems and use the selecct-all checkbox to delete each page worth of problems.)

A more elegant version of this feature would avoid adding an admin-only action, and instead would modify the table-select functionality of errbit so that the "select all" checkbox could be made to apply to all selected problems regardless of which page of search results they appear on.

Comments about this proposal, or about the more elegant proposal, are welcome.