Add future for parsing boolean config args that include a space delimited value.

This does not parse correctly:

```bash
./configVarBooleanSpaceAfter --x true
```

These forms do work for booleans:

```bash
./configVarBooleanSpaceAfter --x=true
./configVarBooleanSpaceAfter --x
```

The space delimited form does work for other types that do not support the implicit value (--<var name> is a special case for booleans).