Implement better media synchronisation

[petrklus]

We own a few projects that have their media libraries sizes ~3-5GB range. While this is way within the allocated storage on the Divio platform, the divio project pull media is already quite unusable - takes a very long time to complete to start and often fails.

We have resorted to using aws-cli and their aws s3 cp command, which works absolutely fine for both pulling and pushing media.

I believe the above should be an integral part of the divio-cli. Its media pull is simply useless for any normal project that has a few media assets in it and fishing for keys in unsupported control panel does not seem like the best solution, not to mention the need to maintain aws-cli and corresponding keys etc.

Please improve the media pulling functionality / at least integrate a way to easily output the full aws s3 cp command for manual running.