Create a separate application to process email generated from the app

[ajburley]

Create a separate application which checks the email inbox linked to the app and processes emails received that are in a standard format that was generated from the app. In particular, it:

• Calls the GitHub API to raise an issue where the user has submitted a defect/suggestion in the app (via the feature implemented in #30)
• Calls the GitHub API to raise a PR where the user has submitted or verified translations in the app (via the feature implemented in #45)

This will be in a separate repository, which is why this issue is marked as a non-code issue against this repository.

The application can be expanded in the future to deal with future features, such as VoC.

Initially everything will be verify-before-send, until we figure out how best to deal with spam. Possibly, spam handling could be improved by having SealNote Plus generate a client certificate, and once we trust that certificate, allowing future signed requests to go through without verification. This would mean we only need to manually verify the initial request(s) from a given client. Also, some simple requests, like upvoting in VoC (see #47), may not even require manual verification.

[ajburley]

Blocked by either #30 or #45, but it's likely #45 will be implemented first.