This adds a "settings" option that allows the user to configure the
board size and target tile, and optionally save them to a config file.
Closes#3219.
Look Ali, it's simple:
* The *model* (in many cases, an instance of GUI::Model, but it doesn't have to
be) should implement the "business logic" (in this case, game logic) and
should not concern itself with how the data/state is displayed to the user.
* The *view*, conversely, should interact with the user (display data/state,
accept input) and should not concern itself with the logic. As an example, a
GUI::Button can display some text and accept clicks -- it doesn't know or care
what that text *means*, or how that click affects the app state. All it does
is it gets its text from *somebody* and notifies *somebody* of clicks.
* The *controller* connects the model to the view, and acts as "glue" between
them.
You could connect *several different* views to one model (see FileManager), or
use identical views with different models (e.g. a table view can display pretty
much anything, depending on what model you connect to it).
In this case, the model is the Game class, which maintains a board and
implements the rules of 2048, including tracking the score. It does not display
anything, and it does not concern itself with undo management. The view is the
BoardView class, which displays a board and accepts keyboard input, but doesn't
know how exactly the tiles move or merge -- all it gets is a board state, ready
to be displayed. The controller is our main(), which connects the two classes
and bridges between their APIs. It also implements undo management, by basically
making straight-up copies of the game.
Isn't this lovely?
