Show values of text datasets in title of render view

I added a --show_text option, which checks each entity for datasets containing text. The text gets drawn in the "title" area, see screenshot.

I also added a little change to render robot in gray to distinguish it from fish. This works by checking the "category" of the entity. According to the RTF, "Canonical values for category are organism, robot, and obstacle." Robot is gray, anything else, including missing category stays the same. I am open to other solutions, I just want to know which one is the robot.

(In the screenshot "R" is the name of the entity, which contains two datasets containing text.)