Add support for export/import to Bitbucket snippets

[GentlemanHal]

Feature Request

What would you like to be able to do?
Backup and restore configuration to Bitbucket.

What problem would it solve?
Many companies use the Atlassian suite for project management and source control. Allowing them to backup configuration to Bitbucket would stop them having to create a GitHub user (or use an employees personal GitHub account) to safely backup configuration remotely.

https://developer.atlassian.com/bitbucket/api/2/reference/resource/snippets

[joejag]

There's a Docker image for running it locally: https://bitbucket.org/atlassian/docker-atlassian-bitbucket-server

I'd recommend we only implement this after moving to server-side gist/snippet calls