Attached is a patch that adds a customization variable for setting which characters you can use as bullets in plain lists.  Unicode has all kinds of pretty characters like ❧ or ☞ that would be good for bullets, why limit ourselves to just [-+*]?

The variable's "set" function sets associated other related variables, regular expressions using it, treating "*" specially since it isn't a plain-list bullet at the beginning of a line.  Care is taken that the character "-" does not wind up in the middle of the character range (but there isn't special processing for "]", and maybe there should be).

I put in some example sets to choose from in the customization menu, though they probably will not be usable since I understand Org-mode still has to support emacs versions that don't support Unicode.

Please take a look, see if it's worth adding, tell me what else I need to do if necessary.  Thanks!

~mark