Cleanup DApp notifications

[franckc]

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Description:

This covers DApp fixes for #810 - fixes to the notification server will be handled as a separate PR.

• Updated notification logic to include all offer statuses and to filter out notification based on party that initiated the action.
• Added unit test to cover new notification types
• Tweaked a bit code in marketplace tests to make it more explicit what account was being used.
• Cleaned up Notification model
• Updated origin-js doc

Checklist:

• Test your work and double-check to confirm that you didn't break anything
• Wrap any new text/strings for translation
• Map any new environment variables with a default value in the Webpack config
• Update any relevant READMEs and docs

[micahalcorn]

@franckc see this and probably this can be closed.

[franckc]

Thanks for pointing this out. Makes sense - we want to protect against invalid offers.
Will add comment.

Will also add checks in other places of the notification code to harden it further: when fetching listing in this method, and also at the adapter level in the getNotification method (for ex an invalid IPFS Hash could cause that layer to error out).

[nick]

Looks good to me. Nothing stands out as an issue, though I'm not super familiar with this part of the code