this changed the CLI flag to use the username instead of the userID
leaving the underlying database function as is.

also now posts are all deleted with no option to skip as this is likely
never needed.

CLI only but backend supports calls from app.db.DeleteAccount already

takes --delete-account user_id_number with optional --posts to also
delete posts. if --posts is omitted all user posts will be updated to
anonymous posts

This runs `go fmt` on changed files and moves around some blank lines.

Ref T613

- Adds a new interface, Apper, that enables loading and persisting
  instance-level data in new ways
- Converts some initialization funcs to methods
- Exports funcs and methods needed for intialization
- In general, moves a ton of stuff around

Overall, this should maintain all existing functionality, but with the
ability to now better manage a WF instance.

Ref T613

Now the func takes a username and password instead of a single string.

This exposes setup and admin functions in the writefreely package, and
uses them in the main application, initialized by the flag parsing that
now happens there.

This is the first step towards making `writefreely` usable as a
standalone package.

Includes app config and some initialization