This commit also add a new string logintoaccount to make the login
button more clear.

This introduces a new "controlled link" file type where the file is not
stored in Moodle - but Moodle will control the access permissions on the file.

Plugins can "freeze" a filearea which means Moodle will take ownership of all the remote
files of this type.

When accessing a file, if the "filebrowser" infomation indicates the current user can write to the file, they
will be granted temporary write access.

Part of MDL-58220

When linking - add the moodle account to the file and
organise it on the moodle side. Also allow read access with link,
but don't make any other changes to the perm/ownership.

Part of MDL-58220

Frederic Massart authored Feb 25, 2015 and Adrian Greeve committed Apr 10, 2015

Part of MDL-45774

Frederic Massart authored Feb 25, 2015 and Adrian Greeve committed Apr 10, 2015

Part of MDL-45774

Strings are not used in the components where they are defined.
If they are used in other components they should be defined in appropriate locations
since the translation may depend on the subject that is being hidden.

Created one function that handles file update to be used from both JS and nonJS filepicker

- get_file should have a request timeout and throw an exception with the details (i.e. timeout reached) if download can
not be completed
- corrected phpdocs

MDL-33136 Dndupload filemanager - user asked to rename/overwrite file when droping file with existing name

- do not die with fatal error if source file in moodle internal repository is missing;
- moved code duplication for moodle repositories into class repository (functions send_file, get_reference_details, get_file_by_reference, get_file_reference);
- update file status after repository::sync_external_file so we know that it is missing (or not missing anymore). Do not run this function more than once for file within one request;
- display readable name for Private Files and Server files with the new format;
- display broken icon in filemanager if we know that source is missing, display information (for admin) where it was located before: see repository::get_reference_details() and extending classes;
- removed unnecessary queries in stored_file::sync_external_file();
- syncronize files before displaying it's size in mod_resource, do not query  directly

- 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

- fixed displaying and dragging of dialog popups;
- fixed error when repository results are filtered;
- added string for image dimensions

- 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)

- Filepicker window is now resizable and draggable;
- filepicker&renderer: removed id substitution from renderer, replaced it with classes (better readability);
- filepicker: allowed tree and table view for search results;
- filepicker: fixed small bug with displaying external link checkbox
- filepicker: display additional information about file in select window, repository returns more formatted information