Added README, definfo.py, shred.py

 - added README.md
 - added definfo.py to retrieve information of DEF files
 - remove shredding option from defextract and lodextract
 - added shred.py which modifies PNG images or directories of them
 - support DEF files with different full width and height in individual
   frames (only ovslot.def)
 - removed common.py