Fix for http://github.com/dpp/liftweb/issues#issue/149

Allows sending static forms as json forms. It also works with regular json forms generated by SHtml.jsonForm but in this case  Lisft generates its own form ID so we'd have to extract it from the <form> node, perhaps with something like:

  def makeJsonForm(html: Group): NodeSeq = {
    val formId = "none:
    val form = jsonForm(json, html)
    form match {
      case Elem(_, "form", attributes, _, c @ _ *) => formId = attributes("id").toString
    }
    form
 }

However SHtml.submitJsonForm is easier to use having simple forms with user provided ID's. See below an example.
For ajaxForms there is also a little helper: def submitAjaxForm(formId: String)

Having a static form like:

	<form id="json">
		<input name="name" type="text" />
		<br />
		<input name="value" type="text" />
		<br />

		<input value="Bike" name="vehicle" type="radio" />
		<input value="Car" name="vehicle" type="radio" />
		<input value="Airplane" name="vehicle" type="radio" />
		<br />
		<select name="cars">
			<option value="volvo">Volvo</option>
			<option value="saab">Saab</option>
			<option value="opel">Opel</option>

			<option value="audi">Audi</option>
		</select>
		<button type="submit">Submit</button>
	</form>


Used something as simple as <a href="javascript:;" onclick={SHtml.submitJsonForm(jsonHandler, "json")}>Press me</a>

Will send the Ajax request containing the json-ized form.