Add enchantment templates to SRD

[arbron]

There are a bunch of magic items in the SRD that can be categorized as Base Weapon + Enchantment. Rather than having a bunch of duplicate items in the compendium, we should instead represent these as items with an enchantment that can then be applied. For example, we could create a "Flame Tongue" enchantment item that applies the extra damage, attunement requirement, changes the rarity, and adds to the name and description.