Feature: table appearing multiple times in select query results

[Diggsey]

Mostly creating this issue so I can subscribe to it.

Possible implementation assuming no significant changes to diesel:

// Internal
struct Alias<To, Id>(To);

impl<To, Id> {traits} for Alias<To, Id> {
    ... {forward to "To" implementation of traits}...
}

// External
define_alias!(Foo, Bar);

// Expands to:
struct FooId;
type Foo = Alias<Bar, FooId>;