This reverts commit 13d10be.

basename will strip the first character if it is accented.
This commit add the mb_basename function, taken from https://bugs.php.net/bug.php?id=37268

This fixes:
- file renaming on upload when a file with the same name already exists
- comments and permissions ("éa.jpg" and "a.jpg" used the same file for comments/permissions)
- photospheres folder ("éPhotoSpheres" was matching "PhotoSpheres")
- file and folder name on the right menu
- file and folder name in the rename textbox
- filename in the left menu, the header and the RSS file
- filename when downloading a picture or a zip

The only remaining problem is with the exif infos on the right menu, but it is an external call to exif_read_data().

This add title for buttons on the ImageBar, RSS and right menubar.

The spinnger was generated on http://spiffygif.com/ with the following parameters:
- 8 lines
- corners 1.0
- trail 50
- rotate 0
- no shadow, halo
- black foreground, white background
- length 0
- width 10
- radius 18

Their license (at the bottom on the "Docs" tab) permits to use it on this project.

Some keys (left, right, up, space, escape) are always listened, making writing
or moving inside the rename input or comment textarea difficult.
This fixes thibaud-rohmer#248.

Before this commit, Menu::list_files() was returning only files considered
to be an image or a video, even with $hidden set to true.
Now we can get all the files a directory contains with a new option, in case
some code expects the previous behaviour.

…erything*

Now that Menu::list_files() is fixed, we can use it to effectively delete
everything, e.g. a thumbnail folder containing xml metadatas among others
files.

The return of self::Extension($file) was incorrectly checked, thus returning
the 0 at the end of the function.
This can cause problems, because `"foo" == 0` is true in PHP...

When a file or folder was renamed or deleted, its metadatas (tokens,
xml and thumbnail) were kept.
This commit will keep the Thumbs directory consistent with the picture
directory.

There is now a new div (#image_panel_table) inside #image_panel, encompassing
#bigimage and #image_bar.
This change was made to have dynamic resizing inside #image_panel, which
will help to display description (see next commit) with a variable height.

It should not change the page rendering, with the exception of a picture
displayed with a page height under 300px. Instead of reducing more and more
#image_panel, now a scrollbar appears.

This new feature is optional (but activated by default).
A new option added to the right menu permits to write a description, displayed
between the image/video and the navigation buttons, or under the header for a
folder.
When a description is empty, it is hidden using CSS to remove its padding.

The Description class is based on the Comments class.

When a comment or a description contained an ampersand, their saving was
throwing a warning:
"PHP Warning:  SimpleXMLElement::addChild(): unterminated entity reference"
An XML with an empty content ("<content/>") was created.
This fixes this problem; a thorough explanation can be read here:
http://stackoverflow.com/a/555039

The change in Video.php to set a width was mandatory for 4:3 screens,
otherwise the video stretched outside the screen.