This is done to enable backup functionality in the admin interface while
we're waiting for the libsqlite-sys 0.17 to bubble up in the upstream
dependencies. Then we can start using `VACUUM INTO`
This also extends the check for the sqlite binary to also try `sqlite3`
as this is the name of the binary in baseimage distributions we use.
This includes migrations as well as Dockerfile's for amd64.
The biggest change is that replace_into isn't supported by Diesel for the
PostgreSQL backend, instead requiring the use of on_conflict. This
unfortunately requires a branch for save() on all of the models currently
using replace_into.
