Fullscreen mode, Remappable keyboard controls + UX improvements

Hello again,

I've been taking a much needed break but having received more feedback I decided I had enough things to fix and improve to create an update.

• New menu layout.  All options from the pause menu are now accessible on the main menu and on a separate menu.
• Keyboard controls can now be remapped as desired.  If you assign a key that has already been used it will simply swap the mappings.  These are of course saved to your game data file.
• Footstep sounds  can be turned on or off.
• Fullscreen mode available in the options menu.
• Added a load screen so as to not make the game feel like it's frozen when loading larger levels.
• Added control bindings for looking and shooting with the keyboard which can also be remapped as desired.
• Fixed missing collision and disappearing scenery on level 5.

So there we go.  A fairly minor update but hopefully for any new players it should make the game more accessible and any existing players will hopefully find the game a little more polished.

All the best to everyone and thanks to all of you who have played/been playing the game.  More will be incoming soon.

Liam