OPAL: add images on the decision tree

[panterz]

Added images as options, like this:

[img:name.png]

and also info for the question that will appear as hint

[panterz]

The decision tree can have images now. The idea is that I prepared a csv like this. The idea is that I can add info as element and the text as information or an image. Moreover I can add an image as field as I described above.

The zip file is uploaded to the server through the survey designer and is downloaded in the app where it's unzipped on a folder inside the folder of the editor. Here's an example of the dir structure:

editors/
           public/
                     <sid>.edtr
                     <sid>/
                              <sid>-1/
                                           image1
                                           image2
                                           image3
                                           sid-1.json

[panterz]

Tested and working