use arguments of storage to generate accumulator default value

The storage is passed as a value to the histogram, because it allows the storage to be configured at run-time.
```
auto h = make_histogram_with(dense_storage(), ...);
```

So far we have not made use of this feature, but I propose to extend the `storage_adaptor` so that it accepts arguments in its ctor which are used to initialize the default value for its accumulator.
```
auto h = make_histogram_with(dense_storage(3), ...);
```
Internally, the storage creates a value `int default_value{3}` with the arguments passed to it. Then, whenever the histogram resets the storage, the accumulators are initialized to this value.

This feature allows one to pass run-time configuration to the accumulators, which is currently not possible.

@henryiii @jpivarski any thoughts?