Removed Grid class (useless)
Refactored CtS, Target and Position

- Position no longer depends on Grid (removed)
- Target no longer has a default (random) constructor) -> moved to CtS
Creation of the class InvalidShotExecption and update all the others

- InvalidShotExecption has been added to throw an error when the shot is
out of the area.

- CTS is now improved

- Display and ConsoleDisplay have a new method to display a message of
an error.