std.format with wstring and dstring

[Richard (Rikki) Andrew Cattermole]

std.format is on my list of modules that I want replaced.

Its written with a lot of error conditions, rather than just adapting to 
the inputs. Hence lots of potential for exceptions being thrown that 
don't need to be.

Multiple multipliers in ``formattedWrite``: format string, output range.

What I'd like to do is to force IES for one or more values, if you want 
finer grained control you want do one value a time (``formatValue``).

```d
writeln(i"$i ${i:X}: $(j + 1)/${(j + 1):X} $1 ${0:X}", k, obj, "atend");
```

Require the use of a string builder, rather than any old output range.
This is a required change for pretty printing. It requires the use of 
arbitrary inserts and removals that ranges can't do.

Every template parameter like these that you have is a multiplier of 
instances, and that isn't good for compile times. Simplifying them down 
may seem like a pain, but it helps quite significantly. Given that there 
are some clear requirements and use cases we can in fact simplify it 
without hurting anyone enough to care.