modify cp_files view and re-export to cp_content.module #1495

#1495 

### Changes:

* "Used in" column is sortable, but only shows the first node the file was used in.
* "Type" filter is exposed to users (i.e. Document, Image, Audio...)
* "Sort by" widgets for date and filesize are removed, instead using sortable table headings.
* First column given a heading label: "Link to share"
* "Edit" and "Delete" columns reduced to "Manage" column (takes up less horizontal space)
* "Upload date" format modified from "long" to "medium" (takes up less horizontal space)

### Before:

![screen shot 2013-10-09 at 12 54 33 pm](https://f.cloud.github.com/assets/228733/1299490/8d9a1e14-3103-11e3-80be-6c99c8ea1179.png)

### After:

![screen shot 2013-10-09 at 12 27 29 pm](https://f.cloud.github.com/assets/228733/1299534/a817cc7c-3104-11e3-9b33-d5e270358e61.png)