Added next-move in replays (incompatible with old replay-files)

Quick Briefing:
gs.c (added nextmv field in GameState, (de)serialization adopted)
tui.c (displays next-move right after previous-move in replays)
tui_skin.c (some irrelevant color-changes)
main.c (netxmv of prev gamestate gets updated in _do_play_board())
replays/ (added new sample replay-files, deleted old ones)

* Ελπίζω να μην τα κάνω μαντάρα :P 
Σε λίγο θα κάνω κι ένα Version Bump commit σε αυτό το branch, με tag "v0.3a3" και θα σου το ξαναστείλω.