Add in-game categories to the achievements

[RenegadeLucien]

From #15. Achievements should be marked with the category they are listed under in-game. Additionally, they should be sort-able by these categories.

[Californ1a]

-Adding the in-game categories to the achievements...I can do that...but it would take some time because I'd have to add metadata to all nearly 3,000 achievements in the database. Not to mention, some of the achievements in the database (e.g. quests) aren't actually full achievements in the game but are more stepping stones, so they wouldn't really have a category.

The ones that aren't in any in-game sections could just be listed under an "Other" or "Not Categorized" section. Alternatively, you could create your own sections for these, for example, "Quests", though I'd say anything like that should be a subcategory of an "Other"/"Not Categorized" main category.