Change BP_GAME_MODE => GameModule created/destroyed as reqd (no ModuleManager).

Preserving GameStatistics (for now) incorporating GameScorer. Rm GameMessageIn
 & GameMessageOut, now have CMessageDisplay + can override CreateGameModule.

Text prompts in pure virtual DrawText. Subclass CScreenGameModule renders using
 big CDasherScreen::Labels, green/red-strikethrough/black in white box,
 aiming for LP_DASHER_MARGIN space between text and Y axis. (Could be improved?)

Misnamed WordGenerator::GenerateChunk returns phrases/lines, false=EOF=end game.
Default FileWordGenerator parses file first to locate all line boundaries,
  then seeks to random (not-previously-chosen) line start. TODO needs srand()ing

Game mode stats per-sentence. TODO: would be much better as part of user-trials,
 indeed user logging ought to be made a special case of game mode, as they
  have much in common (and only game mode tracks locn of target sentence atm)

TODO No di...