Add Windows lib files instructions
Fix Win32 build
Update ignores
SDL_mixer library location fixes
Add assets env variable path location

Assets may either be loaded from relative gfx & sfx paths or from a path
specified in the environment variable VAMPIREIVO_ASSETS.
Update README file

Add build and installation instructions.
Minor text changes
Update readme files - Win32 build
Gamenow  runs in a centered window
Update SDL_SetVideoMode flags
Refactor log messages using stringstream
Add assets env var constant