Add pins to heatmap result statistics, make opacity/saturation configurable

[jxjj]

This adds pins to heatmap results display, and allows presenters to adjust the opacity and saturation of an image to make the heatmap/pins more visible.

Also:

• adds some typing to Question and Response types
• fixes an issue where no alt would show for image heatmap. There's no image_alt property on heatmap question info, just image_name. Using image_name as a fallback for now, but see Allow users to set alt attribute on Heatmap question images #726
• fixes an issue where resizing the window wouldn't update the heatmap/pin location
• fixes a type issue with hideWordcloud. (Technically, I guess there could be problems when evaluating responses.hideWordcloud since responses could be an array?)

Questions:

• Since this is now a pin/heatmap style question, should we update the name? Other ChimeIn like apps call it something like "Drop Pin" or "Pin on Image"... but these don't have heatmaps afaik.
• Should the response input be updated to use a pin icon rather than a red circle for visual consistency?
• Do we need to do any fuzzing of coordinates so pins don't overlap? (My thinking is no, since heatmap would reveal multiple clicks on the same spot).
• Better layout for range or checkboxes? It looked strange above the image (there are a lot of control boxes on the page). Should we hide them behind a button?
• Are there better defaults when showing results? I wonder if 50% saturation and 50% opacity is better than 100%/100%?

Test screenshot still needs to be updated

[jxjj]

btw, on dev for testing

[cmcfadden]

Code change itself looks good - when I'm back in the office, let's do some brainstorming on name (or name change) and how to default some of the controls.