Stats: add support for printing the table, as it is shown on the screen
Remove all uses of KeyEventFilter.

Use the standard QShortcut instead (possibly combined with a
QSignalMapper).
Remove the KeyEventFilter class
Arbitration: use a standard shorcut to select all the players
Arbitration: always show the context menu entry to assign the selected move.

Even if no move is selected, it can help the user to become aware of the
keyboard shortcuts.
Arbitration: rename a few methods
Arbitration: make the shortcuts for assignments translatable
po: detect Boost format strings.

It would be nice to use the --qt option as well, but is is exclusive
with --boost. So we use only --boost, which cannot give false positives
with Qt strings...
Results: add a isEmpty() method, and use it where possible
Ncurses: remove the useless "player" column in the history view
Tests: remove the useless "Player" column in the game history
HistoryWidget: compute the player ID instead of getting it from TurnData
TurnData: remove the m_playerId member