UI refactor pt 4: Task & Task files

Rewrote Task detail page. Also removed the previous file browser--it's now built in to the Task page, completely browsable and bookmarkable/sendable.

The Task view has a base template and then each component of the page (history, files, etc) are rendered through events so we don't have to juggle a load of partials and re-render the page a million times.

There are also 2 sub-views to take logic out of the main view:

* FileBrowserSubview
* ExpandableTableSubview (it will be extended and reused for the Request detail page)

Also added a way of suppressing default error messages when you want to handle them yourself by calling `app.caughtError`.

@tpetr @wsorenson