Embedded digital objects

Here is some basic file embedding functionality for the public app. I don't think we have a full set of business rules to apply to the various permutations of file_version, but I had a look at LOC and came up with a minimal set for now: if the file version is cataloged with type of 'jpeg' or 'gif', and its 'xlink_show' attribute is 'embed' and its 'xlink_actuate' attribute is 'onLoad' and its size is cataloged as less than 500KB, it gets embedded. Otherwise it doesn't.

I also went ahead and created a spec directory for the public app.