Rewrite command line interface

This MR:

• implements proper sub commands (fixes #216 (closed))
• adds full bash completion (fixes #164 (closed))
• let command classes handle their own specific command line arguments
• let all builders clean their install dir before filling it (until now some did, others didn't)
• don't clean by default, but allow to set always_clean in clickable.json, --clean as cli argument or CLICKABLE_ALWAYS_CLEAN as env var
• add chain command that is called when no command is specified (clickable) and can be used to chain commands (e.g. clickable chain install launch logs)
• add command line arguments to create command (fixes #236 (closed))
• removes clean-build command (run clickable build --clean instead or set env var or setting in clickable.json)
• removes deprecated stuff (some params from clickable.jsons, old placeholder syntax etc.)
• setup command checks whether docker setup is necessary before repeating it
• setup command sets up bash completion