Enhanced settings screen: physics ticks, version info

Settings screen:

• Added an option for the number of physics ticks per second - the default is 600 ticks/s and should be used if possible as is guarantees required precision. But for older machines, this setting might be too high and slow down the whole game. In that case you can set it down and still play (with more inaccurate collisions).
• Added a version information at the bottom-right. This helps me figuring out regression effects easier.