A game always starts at the zeroth tick

[richelbilderbeek]

Currently, when creating a game one needs to specify the tick (i.e. the frame number) the game is at:

# From game.h:

  game(const environment& the_environment = environment(),
      int num_players = 3,
       int n_ticks = 0,
       std::size_t n_shelters = 42,
       int n_enemies = 1,
       int n_food = 1,
       int seed = 0
       );

It makes no sense to make the game start at the -say- 1234th tick. Hence, it makes no sense to bother the user/programmer to be able to specify this.

• Remove int n_ticks = 0, from the game constructor arguments in game.h
• Remove int n_ticks, from the game constructor arguments in game.cpp
• In the game constructor's initialization list, replace m_n_ticks{n_ticks}, by m_n_ticks{0},

When doing this, there will be tests that fail. These tests fails because a game is constructed with a certain n_ticks value (that will be zero). Fix those tests, by removing the -probably- 0, argument.