Changes:
* Remove the 'Move Files' button and enable multi-file drag and drop file moving
* Position the 'Delete selected files' button under the checkboxes and make it turn red on hover
* Add 'Ctrl' and 'Shift' range selection to file checkboxes
* Add 'X' delete links to the right of each file
* Rename the 'Save' button to 'Save folder name' and don't show it when listing 'assets' folder since it can't be renamed
More info: http://www.silverstripe.com/google-summer-of-code-forum/flat/1607
(merged from branches/gsoc)
git-svn-id: svn://svn.silverstripe.com/silverstripe/open/modules/cms/trunk@41927 467b73ca-7a2a-4603-9d3b-597d59a354a9
