small additions (new build uploaded)

Made some small additions.

1) In game cheat/debug console, implemented the following https://github.com/Moolt/UnityIngameConsole
2) a basic menu to select the levels
3) the shield can now be used, well very basic in that it is in your hand but it is a start

Those changes aren't in the build that is currently uploaded though.

I've uploaded a new build that includes the latest chances. Use "escape" to open the level select menu and TAB to open the console :)