Now reads in the file and displays contents

Some bugs around the order of filling the plist elements to fix, but
parser is mostly done.

Next steps (after fixing parser bug) is to allow for editing elements
in place, and for adding and removing elements.

Also would be good to make the child rows indent underneath each other
like XCode's plist editor does.

Needs to have a disclosure triangle so that the child rows can be
collapsed as well.