Provide better experience for not logged users.

[pociej]

MOTIVATION: We want provide as simple way as possible for newcomers (not to gvmkit only but golem as whole) to use .gvmi images.

• There should be way to by one command gvmkit-build push temporary image to registry
• gvmkit-build <image_name/or path to dockerfile or/ docker tag existing on dockerhub > --push --nologin
• It should return hash or maybe better temp prefixed tag.
• temporary images should be removed after predefined amount of time.