Engine is not isolated by default

Right now, it writes to Documents/My Games which is something you do NOT always want when developing the engine or having the engine in portable mode here. The game is responsible with regards saving location, not the engine itself.

The issue names no files, tests, or entry points. Begin by locating the engine's default Documents/My Games write path and the portable-mode handling; done means the engine no longer chooses that location by default and the game's save-location responsibility is preserved.

Written by the indexing model from the issue text.