FTP client (utils.ftp)

FTP client designed to be used for log depot testing but it can be used for anything.
I also added automatic negotiation of the time difference between the local and remote computer, so it can be used for precise testing of the time when were certain files uploaded.

More info in docstrings.
Log depot testing (work in progress)
Some fixes

* Repaired depot_type getter
* Added unconfigure before the main test to run with <No Depot>
* Added assert messages to all asserts in ftp client