Selectability of existing sounds in Gallery of Play Sound block

[Jaqster]

In our usability study, we noticed that many students had trouble understanding how to select existing sounds from the Gallery in the Play Sound block. They would click the Play button, but not realize they could click on the entire row to select it. Our recommendation would be to add some sort of rollover effect or animation to make it clear that students can select a sound this way.

[clkantner]

@riknoll based on design crit, I believe we are going with the split button approach for this.