Refactor/all stores

[chrismclarke]

Additional refactoring to remove direct references to firestore and bring all stores in line with databaseV2 methods.

Main Changes

• Improve module store and bindings to make db and activeUser available to all child stores (avoid store.rootStore.stores.userStore method previously
• Change userStore, howToStore, TagsStore, EventStore to use new DB
• Remove legacy database files

Breaking Changes

• User profile avatar no longer retrieved from user store but standalone method (still found in same file, but really it's a user util function)

[BenGamma]

Tidy up much appreciated, makes a lot of sense to me !

[BenGamma]

Is this normal ? We'll have to populate the tags once in production (the tag list as been updated in the mocks)