remote storage v1

[svub]

Basic plugin's for the syncing system to exchange updates and backup the user's contact book.

• publish updates
• pull updates
• back-up user data
• optionally back-up private key (password encrypted)

[svub]

Implemented a setup-free / open Firebase version. As it's open/unrestricted, it cannot be used for backing up personal data, but to exchange profile updates (pull updates not yet tested). Thus, something permanent and secure is needed, e.g. Google Drive, Dropbox - but also IPFS could work with a pinning service.