Modify HTTP logs in clients for safety and clarity

Refs grnet/kamaki#32

Implement method escape_ctrl_chars
Escape control characters in HTTP data logs
Remove misleading separators from HTTP logs
Remove dysfunctional decoding (kamaki.cli.cmds)

Closes #32

String decoding was used to deal with unicode strings, which were
encoded as "unicode_escape" in earlier steps. The later was wrong and
it was fixed with 18d5b0539dcf146d3b9b23fe8e4f4ade6d6dc867
The present commit completes the fix by undoing the decoding.