RPG demystification, cont'd

* Major beautification of the help bubbles for attribute bonuses added in commit 2f79472. They now serve as the bullets in the `ul` rather than staggering along the right side.
* Updated help bubble descriptions of attributes for accuracy (though see to-dos, below)
* Added direct Wikia links for all classes displayed in the class selection modal, and turned part of the header into a link to the class system wiki page.
* Updated class descriptions to provide more of an end-user experience perspective.

Still to do / consider:

* The "Stats & Achievements" page is ungainly right now, with a huge left-hand column, not very much in the center, and a wildly variable right side depending on the user's Achievements rap sheet. What do people think about splitting this into a "Character" tab with all the game-mechanics stuff, and an "Achievements" tab with information about the user's accomplishments like pet counts and badges?
* I noticed a `[user.stats.class]` (resulting in "wizard" etc.) in the post-class-selection Justin tour, but injecting the same bit of Angular binding there as used elsewhere threw errors or showed up as raw text, depending on the syntax I used. @lefnire might know better how to fix that?
* I'm not 100% sold on how bare the "Choose Your Class" modal is when it first pops up, could be a little disorienting. So I'd be cool with putting some form of the one-liner back in at the top, the unfortunate side-effect being that it gives you ugly scrollbars on the longer class descriptions. Maybe another wordsmith might know how to curtail my verbosity :cat::sweat_drops: