Refactors most code

There was some confusion about which module
was responsible for what. This refactor moves
most logic from the file_database to cloudmanager
and to a new module, payload.

This refactor also introduces json handling in
payload module, which was removed from plowshare-wrapper.
Bumps to version 0.6.0
Removes blockchain crawler.

Datacoin exploring code has been moved to a
new repository: https://github.com/Storj/metachains-dtc