Add date to tx command (RIPD-542)

So the `bitset` is pretty cool, but would it be better to `typedef` the full name to something a little more descriptive? e.g. `Transaction::JsonOptions`.

My other problem is that it takes some simple, but obscure code like `getJson(1)` and changes it into several lines of code to instantiate the `bitset`, and set one or more of the bits.

I get that we don't want to pass a bunch of unnamed boolean parameters to the function, but I wonder if there's a better way.
```
namespace Options
{
  enum Date
  {
     nodate,
     includedate
  };
  enum Binary
  {
     notbinary,
     binary
  };

[...]

   Json::Value getJson (Options::Date date, Options::Binary binary = Options::notbinary) const;
```
... That's just an alternative off the top of my head.