Exhibits view should display and sort by a "modified on __" column

[davidmcclure]

Right now, exhibits just stack up vertically, with the most recently created exhibit at the bottom. NL updated a "modified" column on the Neatline native exhibits table every time a change is made to the exhibit or one of its records. The webservice browse view should:

• Display the modified date in a readable format;
• Automatically sort by that column, so that recently updated exhibits are always at the top of the stack.

[davidmcclure]

Done.