More UI demystification

Let's see if I can remember all the stuff I doofed around with here. Overall focus was on having things show up _where_ and _when_ the user first needs to deal with them, and not before.

* Moves the explanations of attributes from the Character Build section of Stats & Achievements to the Attributes section.
* Hides various pieces of Stats & Achievements if the user has not unlocked relevant features yet. For instance, Equipment and Class Equip Bonus are not displayed until the player unlocks the Item Store.
* Added a popover to describe what "unallocated attribute points" are. **Caveat**: I could not for the life of me get Jade to give me a ? bubble on the same line as the `h5` without its text becoming h5-styled as well. So the text itself provides the popover, which is inconsistent; a user will probably find it only by accident. :confused:
* Tavern: brings the descriptions of contributor gear up to date, and adds a link to the new Hall of Heroes.