Create a new stat for +Weapon Damage

[kayla-glick]

A select few items had a + X Weapon Damage effect in Vanilla. In SoD this number has drastically increased. Right now we track this as a Pseudostat, meaning each item must be implemented manually rather than being parsed from tooltips and stored in the database. This stat is functionally the Physical version of the various School Power stats, so we should consider just creating a proper stat for it and parsing it in the database.

• Create a new stat PhysicalPower for tracking this stat
• Parse the stat from wowhead tooltips like we do other school powers
• Remove manual implementations of the pseudostat and the pseudostat altogether