Add option to delete site package during site deletion

[bkheadwire]

When sites are created, we automatically create a package that includes all of the paths for that site's content and components. When sites are deleted, we don't delete those packages automatically (this is intentional - it's meant to act as a backup mechanism). We should make deleting the most recent package for that site an option when the site is deleted.

[ehdatheadwire]

Closing OG issue and relocating to: peregrine-cms/enhancements#5