Cell image enhancements

Just two enhancements that allow more flexible image setting in a tableview cell.

For example:

```ruby
  def judging_tools_table_section
    {
      title: "Judging Tools",
      cells:
      [{
        title: "Flavor Wheel",
        image: UIImage.imageNamed("flavor_wheel_thumb.png"), # Image sent without a Hash as a UIImage
        action: :open_flavor_wheel,
      },{
        title: "SRM Spectrum",
        image: { image: "srm_spectrum_thumb.png" }, # Image sent with a hash as a String
        action: :open_srm_screen,
      },{
        title: "SRM Analyzer",
        image: "srm_analyzer_thumb.png", # Image sent without a hash as a String
        action: :open_srm_analyzer_screen,
      }]
    }
  end