Fix bug which caused too many ships in randomly generated boards
Fix bug which caused too many ships in randomly generated boards

generator/Levels.js used a global variable to hold a randomly generated
board. This variable was reused without being cleared inbetween function
calls, resulting in the number of cells occupied by ships doubling for
each function call.

This commit fixes that bug and removes the global state.

andereld/progark,andereld/progark