Masterwork

[murderteeth]

Related to #102, in this PR:

• A new crafting materials adventure where, once a day, summoners fight up to 3 monsters in turn-based combat
• A new crafting station where summoners can use the new crafting mats to make masterwork weapons, armor, and tools
• An equipment contract that supports common and masterwork weapons and armor
• A Solidity library containing d20 mechanics and utilities for creating lots of new adventures
• New codexes for tools and masterwork items, updates to original weapons and armor codexes

All masterwork source, tools, and documentation can be found here:
https://github.com/murderteeth/rarity-masterwork