Melee weapons can take wear and tear damage based on their primary material.

They still don't lose their effectiveness when damaged, but that comes
next.
Some math tweaks.
Makes melee weapons' damage respect their own state of damage.
Weapons can be destroyed by accumulating enough damage.
Made weapon damage into a function of its own.

subtitled: HOLY CATS I MADE A FUNCTION ALL ON MY OWN!
Better 'weapon destroyed' message handling.
Made damage degradation more intelligent.
Damage mod tweak.
Makes all the degradation code better.
DURABLE_MELEE items, smarter code, items can be damaged by smashing stuff with them.
Merge remote-tracking branch 'origin/master' into melee-weapon-degradation
Anything made of the proper materials can now be soldered. Firearms can be accurized using the proper kits.
Making firearm wear a bit more aggressive.
Misc repair kit to fix misc materials, better and smarter code and materials handling.

misc repair kit tends to spawn around tools in houses and hardware
places.
Prefix fix and general sewing ability.
Merge remote-tracking branch 'origin/master' into melee-weapon-degradation
Smarter code.
A few more flags and small fixes.
Merge branch 'melee-weapon-degradation' of https://github.com/Rivet-the-Zombie/Cataclysm-DDA into Rivet-the-Zombie-melee-weapon-degradation
Powertool durability.