Refactored Square, renamed number to squareIndex
Refactored board, added resize member function

Moved constructor code to new member function so the board can be resized
during run-time in the future.
Added hasMine member variable to Square
Added isVisited member variable to Square
WIP: Trying to connect QML signal with c++ slot
WIP, temporary commit use Q_INVOKABLES
Fixed initialization of BoardModel
Enabled C++11
Front-end now handles mouse events

Each square now handles left and right button presses and propagates the
data to the main window in QML. This makes it possible to connect the signal
to CPP slots.
Model now supports locking a square and visiting

* If left mouse button is pressed in a square and that square is not locked
and has not been visited before it will now set isVisited to true.

* If left mouse button is pressed in a square and that square is locked
nothing will happen.

* If right mouse button is pressed in a square, that square will toggle
between locked and unlocked unless the square has been visited previously,
in that case nothing will happen.
Added states to the front-end
Added count of mines in neighbouring squares.

When a new board is created all squares get ther mine count updated now.
Merge branch 'feature/populate-squares-with-data' into development

Need to add game rules, game logic and menu now,
the board is more or less complete.