More or less a complete rewrite

* No more hardcoded item ids, rifles are being read from items_game.txt
* Added a configuration file tHeadshotOnly.cfg. This will get generated
  with default values automatically and can be reloaded with the new
  command sm_theadshotonly_reloadconfig
* Removed a lot of convars that have to be configured in the new config
  file now
* The config will get updated automatically with new weapons.
* Weapons that have no scope must be configured manually, e.g. The
  Ambassador.
* You can now modify the damage dealt when doing headshots. This is set
  to 1.0 by default, i.e. headshot do normal damage.
* Added sm_theadshotonly_noscope_body and sm_theadshotonly_noscope_head
  to replace the old sm_theadshotonly_noscope
Minor cleanup