Add list of files above subfolder links in file browser.

In the file browser which will eventually be used for importing
files that are already stored on the server, files in the current
folder are now listed above the list of links to subfolders.
Move file list and folder list into widgets

The file list and Folder list used by the file browser are now
Yesod widgets.
Add CSS stylesheets for file and directory list widgets.

The directory list widget uses multiple columns. Each column is
30 em wide and as many as will fit on the page are used. Need
some javascript or something to choose a column width wide
enough to hold all the subdirectory names.