Work on standardizing terminology

Beginning the work of making standard, transparent use of terms for various stats.

* Health, not HP.
* Gold, not GP.
* Gear, not items, equipment, etc. (If we'd prefer "Equipment" be standard, there's a good case to be made for that. Let me know. Definitely not "items" though, because that's ambiguous with pet-related stuff.)
* "Attack" for weapon experience gain, "Protection" for armor damage reduction.
* Expose the formulae for Strength, Defense, and overall experience boost and damage reduction.

More to be done on habitrpg-shared, coming soon.

(I thought I had an issue ticket out there about this, but couldn't find it!)