Plus42 algebraic expressions update

[Thomas Okken]

Interesting. I'll put it on my list, it sounds reasonable and of course it could be controlled with a setting in preferences so people who don't like it can make it disappear. It's not something I'm going to deal with right now, though, but maybe after Plus42 is done.

Complex numbers in equations are a lot easier to support, that just requires making the parser recognize i.