Add option to have info buttons

[tulir]

Similar to #521, but instead of tooltips this adds info icons that you can hover over to see the text.

{
  "type": "string",
  "title": "Name",
  "options": {
    "infoText": "Your full name"
  }
}

P.S. Sorry for recreating the pull request. The original one (#702) was made from the wrong branch