Added nicer command-line item adding: passing no arguments will enter an

Added nicer command-line item adding: passing no arguments will enter an
interactive more which asks for each property in turn. While I was at it, I
fixed an implementation problem WRT the spec - I wasn't raising a
ValueError if the key property was missing from a create(). Also added a
protected=boolean argument to getprops() so we can list only the mutable
properties (defaults to yes, which lists the immutables).

git-svn-id: http://svn.roundup-tracker.org/svnroot/roundup/trunk@270 57a73879-2fb5-44c3-a270-3262357dd7e2