Spark notebook: display images inline using base64 encoding and HTML injection

[lintool]

Check out this neat trick: http://stackoverflow.com/questions/8499633/how-to-display-base64-images-in-html

This means that, if we go with my suggestion in #177 we could do something like Base64Encode(r.getContentBytes), and then use the HTML inject trick to transparently render images inline in the Spark notebook.

I bet we can find and integrate an open-source face detector, so we can write scripts like "Find me all headshots from NDP in 2014" and display the output right in the Spark Notebook... neat, huh?