MDL-31901: Simple loading of the next page, migrating to YUI 3.5.0

- instead of using paging bar and navigating between pages, there is a link 'more' in the bottom of the list that loads the files from the next page and adds them to the bottom of the list;
- DataTable is updated to YUI 3.5.0, sorting is done properly
MDL-32473,MDL-32471: Lazy loading of next page and image thumbnails when scrolling
MDL-31901: show shorttile instead of title where applicable
MDL-31901: user renderer for filemanager, decrease html generation in filemanager.js and dndupload.js
MDL-31901: moved filepicker html to files/renderer.php, pass templates once per page
MDL-31901: Allow FileManager to re-use FilePicker JS code for view modes:

- when loading core_filepicker we extend the Node element with functions necessary to display files list in different view modes;
- repository/filepicker.js is changed to use those functions;
- FileManager now has three different view modes (icon view, tree view and table view), JS code is re-used from FilePicker;
- files in FileManager no longer have context menu, they have one popup Widget with different actions instead;
- Added more templates for JS code to FileManager, use similar CSS class names as FilePicker;
- lib/filelib.php : fixed double slashes in path, return more data about files;
- lib/form/filemanager.php : pass information to FileManager about available licenses and default author;
- repository/draftfiles_ajax.php : return information about directory tree for file moving UI in FileManager, return formatted information;
- repository/lib.php : function repository::prepare_listing() now can work also with draftarea files listing;
MDL-31901: Change the UI in filepicker CSS rendered and images
MDL-31901: removed accidentally commited testing code
MDL-31901: FileManager, added image for accessing right-click action
MDL-31901: FileManager uses more YUI3 windows and more renderers

- Add folder dialog in FileManager now uses YUI3 and renderer;
- Fixed bug with remembering current folder in Tree view;
- Display error messages in FileManager using YUI3 and not using 'alert'
MDL-31901: Updating/moving files in FileManager

- added new functions to the backend (repository/draftfiles_ajax.php) to allow changing of file name, location, license and author in one request
- enabled changing file properties using JS UI (lib/form/filemanager.js)
MDL-31901: Highlighting main file in FileManager
MDL-31901: Filemanager and Filepicker, cleaned up requirements and strings
MDL-31901: filemanager: fixed 'Original' label, and small bug in treeview navigation
MDL-31901: filemanger: fixed bug with switching to treeview in empty folder
MDL-31901,MDL-28666: add support for external references in new filepicker design
MDL-31901: moved select-file panel outside of filepicker/filemanager for better UI
MDL-31901 filepicker interface changes:

- fixed displaying and dragging of dialog popups;
- fixed error when repository results are filtered;
- added string for image dimensions
MDL-32867 Working with external references in filemanager

- Files that are references to external resources have special shortcut icon in filemanager
- When user selects a REF file in filemanager, he can see the 'Original' of the file in the way that original repository wants to show it, it is loaded dynamically via AJAX request
- Files that are themselves the source of references of other files in the system have 'link' icon in filemanager. When user tries to remove/rename/overwrite SRC file he is warned that all ## existing references will be updated/converted to copies.
- Changed confirmation messages for deleting, moving/renaming of the folders
- confirmation dialog in filemanager is using YUI3 now
MDL-32914 fixed function get_imageinfo() to get rid of notice messages