Style /browse to distinguish folders

* Add small folder icons to the left of folders to distinguish them
  from other files.
* Right align Size, Nlink, and mtime columns.
* Remove 'name' title since it is apparent
* Order files first by file type, i.e. folder or not folder, and then
  by name.

Review: http://reviews.apache.org/r/12887
Compute framework stats in one iteration

Rather than iterate over 'frameworks' and 'completed_frameworks' once
to update the slave mappings and a second time to calculate stats for
the frameworks, move that work into a single loop.

This also removes a 'concat' call that was creating a temporary Array
used to calculate stats once and then thrown away.

Review: http://reviews.apache.org/r/12880
Remove 'ui-if' direction in favor of 'ng-show'

Angular provides 'ng-show' to hide elements when not needed. They are
rendered in the DOM unlike with 'ui-if', but using native Angular
prevents needing outside code or dependencies for a directive used in
only one template.

Review: http://reviews.apache.org/r/12888/