Added graphics option to make soft shadows optional
Added cvar r_useHalfLambertLighting to make it optional, it requires reloadShaders
Sacrificed texture bias option for shadows option. fixes #109

We can't add new graphics options without altering the original Flash menu
files which we don't have. I disabled the r_lodBias functionality which
can make the game look worse by adding a bias to the texture lookup
functions which cause choosing texture mip maps that are smaller than the
original image size in every view even though we want the first mip map
level 0 which is the best quality.
Changed r_useShadowMapping 1: medium+faster, 2: high quality
Make high quality shadow mapping the default