game.sav versioning and sanity

* game::save, game::load: moved iostream stuff to gamesave.cpp

* separated misc / weather / location / killcount / player chunks into
  individual lines, and parse on a line-by-line basis. This makes .sav more
  resistant to complete breakage from adding a monster, or even a player data
  variable ( if those variables are added to the end of the variable hairball ).

* Implement versioning support; if a major change is made to the format, it is
  possible to load previous save versions; saves prior to merging this commit
  should work.

All of these changes will allow easier conversion of individual classes to json
  serialization.