Twos code cleanup

[Riksu9000]

Made the interface slightly larger.
Removed magic row and col counts. The size can be increased to 5x5 for example just by incrementing a value.
Fixed many warnings.
Reduced for loop count. Each either save a few bytes or no change.
Reduced library dependency.

In updateGridDisplay() only a for loop was removed and the indentation changed. The diff looks more complicated.

[FintasticMan]

Wouldn't it be better to use std::array instead of raw arrays? It should be possible to just replace the raw arrays with std::array because nCols, nRows and nCells are constexpr.

[JF002]

I had the same thought, but I'm not sure it'll help to make the code more readable. For example TwosTile grid[nRows][nCols]; would become std::array<std::array<TwosTile, nRow>, nCol>. Plus we are using this array as a simple table, we don't really need methods from std containers.

[FintasticMan]

It seems to me that a lot of the variables here are full (unsigned) ints, but they could just be (u)int8_ts.

[Riksu9000]

I've noticed that sometimes using smaller integers results in a larger binary size. These specifically don't make a difference, but if tryMerge() and tryMove() functions used uint8_t, the binary size would increase. This is why I'm not always sure which is best to use.

[FintasticMan]

Hmm interesting... Maybe with smaller integers the compiler isn't able to do as many optimisations? Anyway, if it increases the binary size, I don't see much benifit to using smaller integers.