Halo 2 maps, every Megalo game type readable, and game types checked before they ship

Added

• mjolnir cache info|tags|stage reads other Halo games' map files. cache info names the game a .map comes from; cache stage stages an MCC Halo 2 multiplayer map for conversion in the same layout the Halo CE converter writes, so tools/level/convert_ce_map.sh converts Halo 2 maps beside Halo CE ones.
• mjolnir megalo dump <file> lists everything a Megalo game type holds: its options, teams, traits, strings and the whole script as triggers with named conditions and actions. It reads .mglo files and MCC Halo Reach .bin game variants, and says whether the file encodes back bit for bit.
• mjolnir megalo validate <file> checks a game type is one the game can load safely. megalo write and map pack refuse to write one that is not.
• mjolnir megalo write --mode team-slayer: Red against Blue, a kill of an enemy scores 1, a teammate kill costs 1.
• mjolnir map pack --game halo1|halo2 tags a map pack with its game for the hub's game filter.
• mjolnir live engine prints the running match's team and player scores.

Changed

• mjolnir megalo write --mode ctf writes a CTF whose blue flag is its own object type (20), so each flag's colour comes from the game itself; --single-flag writes the old one-type script. It needs CE runtime 1.13.0 or later.
• mjolnir megalo write --tick-rate defaults to 60, the game's own rate: at 30, the dropped-flag reset and the health-pack respawn lasted half their time.