Started implementation of slide system for classes

- Added DAO and entity layer for slides
- Added a service to add slide to a class
Started implementation of the new design

- Foundation should now longer be used in the future
  -> Only the responsive grid system was useful, and was already "heavy"
     for what it was used
  -> The application now use its own grid system
- Creation of a Java-like BorderLayout
  -> Used to "fix" the copyright of the standard pages at bottom
  -> Used as main layout for Javascript applications of the desktop
- Started to change views according to new CSS files
- Added some images for menu and logo