Rework flags and manage implements

[xyzzy42]

Big rework of manage implements and the selectedImplements flags. It's half the size of the existing code. The individual commits do smaller pieces and have detailed descriptions.

Main features:

• Removed all the old fields in selectedImplements, e.g. slug, translated name, adept status, etc. They weren't really used anymore. Just the uuids of the selected inventory items are there now. Old actors will just have the extra fields linger around and they'll be ignored harmlessly. Clearing implements will clearselectedImplements totally and make a new one.
• The code for manage implements now gets all the data from the attributes.implements objects.
• New way to check for Thaumaturge class, dual-class, archetype. Should be faster and more reliable.
• Lots of code that searched through items and feats is made simpler and faster, e.g. by directly accessing a feat with item.grantedBy or implements[implement].baseFeat.description instead of searching through all items on the actor. There's also fewer places that do this, so adding dedication support (which is not done here) should mean fewer places to edit.
• Duplicated Hook callbacks for adding REs in each implement are refactored into Implement base class.

[xyzzy42]

Turns out setFlag() didn't work the way I thought it did. It doesn't set a flag to the object supplied, but rather merges the object into the existing flag. Removing an implement flag not on the character sheet anymore needs an explicit "-=impSlug": true in the flags object. Fixed this in latest push.

[mysurvive]

Thanks for doing this. It's something I wanted to get around to eventually but haven't had the chance to.