FTP client (utils.ftp) and Depot testing

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.
Merge pull request #190 from mfalesni/ftp_client

Log Depot testing
Flash improvements (multiple messages, assertions)
Merge pull request #271 from weissjeffm/flash-improvement

Flash improvements (multiple messages, assertions)
Added wait_for_visible in taggable.py to prevent errors
Merge pull request #272 from mfalesni/taggable_fix

Added wait_for_visible in taggable.py to prevent errors
Added new docs section