Fixed tag option for "docker pull" (the option was ignored)
add debug for error in the server
Revert "Client: better progressbar output"

This reverts commit 3ac68f1966222d9a1c0ff867515e3f5c2f83e422.
*Client: Fix the progressbar, without manipulating other outputs

Prior this commit, 'docker images' and other cmd's, which used utils.HumanSize(),
showed unnecessary whitespaces.
Formatting of progress has been moved to FormatProgess(), justifing the string
directly in the template.
CmdAdd and CmdEnv now respect Dockerfile-set ENV variables