DSL add uninstall `:delete` and `:trash`

- `:delete` is intended to replace `:files`
- `:trash` is intended to move files to the OS X Trash
- `:trash` is only a stub — currently all three function identically

References: #4688
Merge pull request #4928 from rolandwalker/unininstall_trash_delete

DSL: add uninstall `:delete` and `:trash`