Changed "Metadata" to "Content" so that fields show up in CMS

Changed Metadata to Content as the Metadata field is gone in 3.1.
Exclude _versions folders

Exclude versioned folders from lists.
To do: detect of Versioned Files module is installed
Added clear list option to drop down field
Moved position of fields, added versioned files filter

Moved fields under Content, check for VersionedFiles module to exclude
"_versions" folders from listings.
Merge pull request #5 from tardinha/master

Changed "Metadata" to "Content" so that fields show up in CMS