significantly improved autocompletion by simply prosponing stepping down in command syntax tree in choices_left method. Also replaced newline character by empty string as EOL marker. Maybe not the smartest move either.. anyway, by delaying the traversal step when parsing incomplete input for completion, the problem of autocomplete results overwriting their direct predecessor seems to be gone. surprise.
Got autocompletion to 'complete' complete terms as well, thus indicating their validity. Also, handled empty input line so that hitting tab without having entered anything shows available commands.
Merge branch 'debug'