Improve melee weapon generation

[angelusmetal]

• Tweak trait scores
• Tweak range & speed; type should depend on that (e.g. daggers have lower range, but higher speed; slower weapons have more reach; some weapons have higher spread, which may land blows that don't do much but others that do a lot).
• Think about whether material affects anything - not damage (otherwise all high level weapons will look the same)
• Weapon effects (not just name; also affect color)

[angelusmetal]

I did a nice approximation of different weapon types and materials (each affecting weight, speed, how much energy is drained with each blow). There is no "better" weapon type; all of them have pros and cons and scale with weapon score/level. Gold cost does as well.

Also I did a first implementation of fire effect (it can be stacked) by making traits both expirable now, and stackable (they were a fixed set before) and in the meantime, found & fixed a nasty concurrent modification bug.

[angelusmetal]

Pending work is adding other effects (poison, chill, etc)

[angelusmetal]

Implemented on b973713c7a47abfac39759575e5fb79bfb320818, 4b53844f730202a9eaae6aad28612870e757b7fe and 7e088dd282279da624d83f101dbd7fa253945c9d