GUI Update: Now SFML calendar is embed in a QT frame and SFML agenda is abandoned. New agenda will only use only QT elements.  This version needed to be integrated in the new version of GUI asap.
Additional changes:
1. Added Boundary checking when dragging.
2. Shortened task name for small calendar blocks.
3. Added function to jump to any task, now pressing space can go to the closest task. Default position is also fixed to show closest task from current time.
4. Added Popup fade-in/out effect.
5. Fixed mouse position checking bug.
6. Fixed block position bug when dragging fast.
7. Fixed click-through-able popup