Improved unknown sprite handling

added generic error sprite
Removed double simple light calculation
Added credits to menu
Added method for multi-line text
Changed brightness values between 0 and 1 instead 0 and 255
Improved text managment
deleted emtpy lines
improved diagrams
Optional PseudoGrey & small changes
New unlit sprites
refactoring
Made new class for pseudoGray and improved rendering with PseudoGray
Put more pseudogray into the code
Removed specular light because it may be wrong
New version number for the LE