Add annotations on the timeline

The user should be able to:

• Create groups of annotation
  • A group has a label, a color and a list of annotations
  • It exists default group defined by a .ini file
• Create annotations on the timeline by pressing keys
  • First key press indicate the start of the annotation
  • Navigate through the timeline with keys
  • On press key, open a input dialog to choose or create a group of annotation
  • The group label of each annotation is shown inside the corresponding rectangle
  • Remove 'F' for fullscreen and use "function" (F1, F2, FX...) key [F11 is the mostly used shortcut for fullscreen]

Bugs to be fixed:

• Adjust number of ticks according to the window width
• Show first image when video is loaded twice in a row
• The timeline must be updated when the slider is clicked outside the cursor