Add Notification system

[renatomassaro]

This PR introduces the in-game notification system. There are 4 types of notifications:

• Server notifications - Notifications bound to a server. Might be gateway or endpoint. Ex: FileDownloadedEvent
• Account notifications - Notifications meant for the player, or that exist beyond a server. Ex: ServerPasswordAcquiredEvent
• Clan notifications - Notifications bound to a clan. Ex: ClanMemberJoinEvent, ClanWarStartedEvent
• Chat notifications - PM or regional messages. Ex: ChatMessageEvent

For this PR we'll add Server and Account notifications. Clan and Chat notifications are out of scope for now.

• [x] The old Notificable system was renamed to Publishable, meaning that outgoing events are publications, i.e. they are published to the client. Referring to that feature as notification is wrong from now on.
• [x] Notificable macros, used to register notifications off of existing events.
• [x] NotificationAddedEvent, used to publish to the Client that a notification has been added
• [x] notification.read and notification.read.all requests
  • [x] NotificationReadEvent
• [x] Include existing notifications on Bootstrap
• [x] Tests
• [x] Typespecs
• [x] Docs

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This change is 

[renatomassaro]

Reviewed 105 of 116 files at r1, 15 of 15 files at r2. Review status: :shipit: complete! all files reviewed, all discussions resolved

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lib/event/notificable/notificable.ex, line 16 at r2 (raw file):

    | Server.id

  # TODO: Rename this method

Rename and add docs

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lib/notification/event/notification.ex, line 151 at r2 (raw file):

      def whom_to_publish(event),
        do: %{account: event.account_id}

Extra line

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lib/notification/model/notification.ex, line 242 at r2 (raw file):

    def validate_id(_, _),
      do: :error

Extra line

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Comments from Reviewable

[sourcelevel-bot[bot]]

Ebert has finished reviewing this Pull Request and has found:

• 3 possible new issues (including those that may have been commented here).
• 1 fixed issue! 🎉

You can see more details about this review at https://ebertapp.io/github/HackerExperience/Helix/pulls/406.

[renatomassaro]

Reviewed 7 of 7 files at r3, 1 of 1 files at r4. Review status: :shipit: complete! all files reviewed, all discussions resolved

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Comments from Reviewable