Clean up blacklist checking logic
Clean up blacklist checking logic

- no longer expecting `this` to be set by HOF
- we're always going to be checking URLs validity against blacklist, no need to have non-blocklist check exposed
- still the same interface for HOF + checking fn
- abstract local storage accessing logic into own function for flexibilty with whatever storage later
- updated all JSDoc

WorldBrain/WebMemex,WorldBrain/WebMemex