Adds redis caching to bb sync script

[bomoko]

This PR potentially takes some of the pressure of the API when doing a bit bucket sync

It pulls the full user list down from BitBucket for every project, creates a hash from the email and permission list currently on that project on the BB side, and compare that to a cached hash (in redis) - if there is a difference, we continue with the sync as usual, if there has been no change to the hash in the last 24 hours, we know we can skip processing the current project.

Checklist

• Affected Issues have been mentioned in the Closing issues section
• Documentation has been written/updated
• PR title is ready for changelog and subsystem label(s) applied

Explain the details for making this change. What existing problem does the pull request solve?

[Schnitzel]

@bomoko can you fix the merge conflict? thanks!