Support Balsamiq Mockups In Viewer

It would not be very hard to do. I inspected the file. It turns out to be another sqlite3 format file. Upon inspection of the database contained within, it just contains ID's to files which have links. Pictures are base64 encoded strings. We'd need our own icon for each type of things. Like buttons, maps, etc. Overall no big deal.

If we use sql.js then we can just query the file for the data we need. Boom

Mainly everything we need is in Resources and Thumbnails. Images are in base64 and data is json data.

cc @tauriedavis @dimitrieh @iamphill

Do people still use Balsalmiq?