Mouse button update.

Changed the way the mouse buttons control the game and added an option to allow selection of what the buttons do to the game board (it is on settings tab 2). Therefore in general (depending on what the buttons did before) you can select primary to rotate and secondary to select etc instead of the default of primary selects, middle moves and right rotates. Note that in making this change that I had to decide whether an action resulting from a button press should change based on the setting, or stay the same because it wasn't related to the select/move/rotate principle - e.g. the buttons fall into this latter category, however some things fell a little between the two, in particular in the workshop screens, and therefore changing the setting may not make everything change to every ones tastes.